Every MLB Team's Most Promising Young Building Block Heading into 2021

The way to build a contender in Major League Baseball today involves cultivating a core of young talent and then going from there.

To this end, every team in the league has at least one up-and-coming star to pin its hopes on.

With the 2020 season in the rearview and the 2021 campaign not too far in the future, we've highlighted every club's most promising youngster. Though we had to make some exceptions, we mostly focused on players who will be 25 or younger next season.

We also wanted to avoid being too obvious, so we chose not to shine a light on young players who have already achieved stardom. Think guys like Juan Soto, Ronald Acuna Jr., Fernando Tatis Jr. and Cody Bellinger.

We'll proceed in alphabetical order by city.

2021 Age: 25

Not much went right for the Arizona Diamondbacks in 2020, but at least Zac Gallen continued his rise.

Gallen began said rise with the Miami Marlins as a rookie in 2019, yet they inexplicably traded him to the D-backs that July. He promptly kept doing his thing, authoring a 2.89 ERA in eight starts for Arizona.

So it went in 2020, wherein Gallen put up a 2.75 ERA in 12 turns. Notably, he achieved an MLB record in August for the most consecutive starts with three or fewer runs allowed to begin his career.

There are more overpowering hurlers than Gallen, who averages "only" 93.3 mph on his fastball. But with good command of a four-pitch mix headlined by a nasty changeup, he nonetheless has the goods to carry on as an ace.

2021 Age: 23

To reiterate, we're not counting young players who can already claim star status. With regard to Atlanta, that means Ronald Acuna Jr. and fellow All-Stars Ozzie Albies and Mike Soroka.

If his first impression is any indication, Ian Anderson will soon be an All-Star in his own right.

Albeit in only six starts, Anderson impressed as a rookie this past season to the tune of a 1.95 ERA with 41 strikeouts and only one home run allowed in 32.1 innings. He also took four turns in the playoffs and allowed only two runs in 18.2 innings.

All this is a testament to not only the quality of Anderson's fastball, curveball and changeup, but also how he uses them to generate both swings-and-misses and ground balls.

2021 Age: 24

At least until catching prospect Adley Rutschman gets the call, Ryan Mountcastle is the best fruit that the Baltimore Orioles have harvested from their rebuild.

Mountcastle arguably should have debuted in the majors in 2019, wherein he played 127 games at Triple-A and hit .312 with an .871 OPS and 25 home runs.

As it is, the slugger's debut with Baltimore didn't come until the 2020 season was nearly a month old. But even sans a minor league season to get ready, he hit the ground running by batting .333 with an .878 OPS and five homers in 35 games.

Though Mountcastle's underlying metrics were less impressive, his above-average marks for hard-hit rate and sprint speed suggest the Orioles indeed have a dynamic player on their hands.

2021 Age: 25

The obligatory caveat is that he's no Mookie Betts, but the Boston Red Sox must be happy with what they saw from Alex Verdugo in 2020.

After a promising 106-game sample with the Los Angeles Dodgers in 2019, Verdugo played in 53 games in 2020 and ended up with an .844 OPS and six homers. He also ranked fifth among right fielders with 1.9 rWAR.

That's partially a credit to Verdugo's defense, which rated as above-average for defensive runs saved and ultimate zone rating.

Granted, Verdugo's generally subpar offensive metrics allow for some skepticism over his bat. But in posting above-average numbers against left-handers in each of the last two seasons, he's at least eased concerns over whether he's best suited for a platoon role.

2021 Age: 24

Here's where there's slim pickings, as most of the players on the Chicago Cubs' active roster are in their late 20s or somewhere in their 30s.

Nico Hoerner is the most notable exception, though now admittedly isn't the most convenient time to sing his praises. He played in 48 games in 2020, but mostly as a defensive specialist.

Indeed, Hoerner didn't exactly hit his way into more of an everyday role. His 126 trips to the plate yielded a frankly ugly .222/.312/.259 batting line.

But if nothing else, Hoerner was a top-notch defender by way of his five outs above average. He also flashed 93rd-percentile speed and a swing-and-miss rate in the 87th percentile, so his offensive future isn't totally without merit.

2021 Age: 23

Meanwhile on the South Side of Chicago, the White Sox are practically overflowing with young talent. But if the question is which youngster hasn't peaked yet, Luis Robert is the obvious answer.

With help from his 96th-percentile sprint speed, he nearly tied for the overall MLB lead by racking up seven outs above average in center field. Rightfully, he got a Gold Glove for his efforts.

Robert has more work to do offensively after getting on base at just a .302 clip in 2020. He struck out in 32.2 percent of his plate appearances, with a truly terrible swing-and-miss rate.

If Robert can cut down on whiffs and make more frequent use of his power, watch out. Because there isn't much question that said power is legit.

2021 Age: 26

The Cincinnati Reds have 22-year-old Jose Garcia at shortstop, but nothing from his 2020 season stands out. Meanwhile, 24-year-old catcher Tyler Stephenson is seemingly third on the club's catcher depth chart.

So, we've bent our rules so that we can talk about Nick Senzel.

His major league experience has so far been one of disappointment, to be sure. He's played in 127 games since 2019 and posted just a .245/.305/.416 slash line. He's also had more than one stint on the injured list.

And yet it wasn't that long ago that Senzel was hitting .312 with an .895 OPS in the minors. And even in the majors, he's showcased 97th-percentile sprint speed with decent exit velocity (88.3) on his batted balls. He may yet become a star.

2021 Age: 23

Even if Cleveland follows through on its plan to trade shortstop Francisco Lindor, it will still have an avenue to contention in 2021 by way of its young starting pitching.

On that front, Triston McKenzie is the youngest yet also one of the most talented hurlers Cleveland has.

After sitting out all of 2019 with a bad back, the slender righty returned to appear in eight games with the big club in 2020. In these, he mostly dominated his way through 33.1 innings, striking out 42 and ultimately racking up a 3.24 ERA.

McKenzie got his fastball as high as 97 mph and also showcased a tight slider. If he can nail down a reliable third pitch, he'll have top-of-the-rotation upside.

2021 Age: 24

Alas, the Colorado Rockies. They're stuck in an uncomfortable purgatory wherein their roster is short on both talent and youth.

The best we can offer is the notion that they might still have something in Brendan Rodgers.

Much depends on his right shoulder. It's been through a lot over the last couple years, as he had season-ending surgery for a torn labrum in 2019 and missed further time in 2020 with a capsular strain. Across the two seasons, he's hit just .196 in 32 games with the Rockies.

Rodgers' minor league track record, however, still contains a .296/.352/.503 line in parts of five seasons. And even as recently as the start of 2020, he was still a consensus top-100 prospect.

2021 Age: 24

Going into 2020, most everyone was anticipating the Detroit Tigers finally calling up top pitching prospects Casey Mize and Tarik Skubal.

When they finally did, the results proved to be...not great. The two youngsters handled 60.1 innings between them and did little of note as they racked up a 6.27 ERA.

The real excitement was on the offensive side, where Willi Castro played in 36 games and quietly put himself on the map with a .349 average, .932 OPS and six home runs.

Though Castro averaged only 85.4 mph with his exit velocity, he hit enough line drives to make up for that. In the best-case scenario, he'll keep that up and become a batting champion.

2021 Age: 24

The Houston Astros outfield doesn't look like much while George Springer, Michael Brantley and Josh Reddick are afloat on the free-agent waters, but at least they have a budding star in Kyle Tucker.

Because he was an elite prospect at the time, it was a big deal when the Astros called Tucker up for his MLB debut in July 2018. But he promptly struggled in the majors, and what strides he made in 2019 were small.

Not so in 2020. Tucker played in all but two of Houston's games and acquitted himself well with an .837 OPS and 27 extra-base hits. What's more, nearly all of his key peripherals finished in above-average territory.

After a year like that, Tucker looks like a do-it-all outfielder with All-Star honors in his future.

2021 Age: 24

Given their limited budget, the Kansas City Royals don't have much choice but to build from within. They were able to do that for World Series glory in 2015, so don't underestimate the core they're building now.

This core specifically contains four 20-something starting pitchers, of whom Brady Singer might have the highest upside.

Singer is a bit of a throwback in that he's a sinker-slider guy, whereas many pitchers have joined a movement toward four-seamers and curveballs. There is, however, no doubting the quality (see here and here) of Singer's primary offerings.

In 2020, Singer made 12 starts and rode his stuff to a 4.06 ERA over 64.1 innings. As rookie seasons go, that's one that portends even better things to come.

2021 Age: 24

The Los Angeles Angels can and should sign some high-priced starting pitchers this winter, up to and including NL Cy Young Award winner Trevor Bauer.

Yet they do have some talented hurlers already in house, of whom we like Jaime Barria the most.

Barria endured a difficult year in 2019, in which he appeared in 19 games and got lit up for a 6.42 ERA. On either side of that, however, are a 2018 season marked by a 3.41 ERA and a 2020 campaign marked by a 3.62 ERA.

With a fastball that sits at just 92.1 mph, Barria isn't going to overpower anyone. Yet he does have a diverse array of pitches, and he showed in 2020 that he can use them to avoid hard contact. He allowed only three "barrels" all season.

2021 Age: 24

If you were to stand in the middle of the Los Angeles Dodgers clubhouse and point in any direction, chances are your finger would be aimed at a 20-something star.

But in this scenario, we're happy to give the floor to Julio Urias.

Young as he is, the left-hander already has five major league seasons to his name. He's pitched well in these, posting a 3.20 ERA over 239 innings. Yet he only recently put himself in the spotlight, as his postseason experience included a 1.17 ERA and the final out of the World Series.

That was a case of Urias showing off an arsenal full of dangerous pitches. All he really needs to do now is show that he can consistently eat more than five innings at a time.

2021 Age: 22

The Miami Marlins aren't even close to having harvested all the best talent from their farm system, so it's a good sign that they were nonetheless able to make the playoffs in 2020.

Leading the charge was Miami's collection of young pitchers, of whom Sixto Sanchez carries a particularly exciting appeal.

Simply put, the guy throws bullets. Sanchez averaged 97.6 mph on his fastball in 2020, and he hit at least 100 mph on 21 occasions throughout the regular season and the playoffs.

The reality that Sanchez struck out only 33 batters in 39 innings during the regular season points to how he needs to work on his location and secondary offerings. All the same, few pitchers can match his sheer power.

2021 Age: 26

On the Milwaukee Brewers' infield you'll find 24-year-old second baseman Keston Hiura and 23-year-old third baseman Luis Urias. Yet it's hard to get excited about either of them right now.

After a strong rookie year in 2019, Hiura regressed to an alarming degree in 2020. For his part, Urias simply doesn't have the kind of power that teams typically like at third base.

So, it's time for another rule-bending so we can rave about Corbin Burnes.

After a brutal time in 2019, all Burnes did in 2020 was post a 2.11 ERA with 88 strikeouts in 59.2 innings. That's life, apparently, when a pitcher throws 96.0 mph with elite spin on both his fastball (99th percentile) and his curveball (95th percentile).

2021 Age: 24

In Alex Kirilloff, Royce Lewis and Trevor Larnach, the Minnesota Twins have three top-tier prospects who could become major league regulars in 2021.

In the meantime, they have a rare sort of player at second base in Luis Arraez.

The 2020 season was basically a "prove it" year for him after he earned looks with a .334 average in 92 games with the Twins in 2019. Though injuries limited him to only 32 games, he did indeed prove it by hitting .321 this past season.

Even if power is never a big part of his game, consistency like that will go a long way. He's also on the up and up defensively, as he went from the black to the red for both DRS and UZR from 2019 to 2020.

2021 Age: 22

Though the New York Mets figure to be active shoppers this winter, they already have a potential All-Star at shortstop.

Or at least, a Gold Glover. Andres Gimenez earned a reputation as a stellar defender as he was coming up through the minors, and he indeed looked the part as a rookie. He was a plus defender at multiple positions, ultimately tallying five outs above average.

On the other side of the ball, that Gimenez finished in the fifth percentile with his hard-hit rate is a fitting testimonial to his nonexistent potential as a slugger.

But if he keeps putting balls in play—he struck out 28 times in 132 plate appearances—while maintaining his 94th-percentile speed, Gimenez can nonetheless earn his keep offensively.

2021 Age: 22

Whether the New York Yankees have yet seen the best of Gleyber Torres is a good question. But since he's already a two-time All-Star, he doesn't necessarily need to get any better.

Deivi Garcia, on the other hand, does need to show the Yankees more after a good-not-great rookie season. He pitched to a 4.98 ERA in 34.1 innings and whiffed only 33 batters in the process.

However, there's plenty to like about Garcia's stuff. He got his fastball up to 95.8 mph this season and also made highlights aplenty with his curveball.

If Garcia can't hack it as a starter, he might at least make for a great late-inning reliever. Such a role would also be less taxing on his diminutive 5'9", 163-pound frame. 

2021 Age: 23

At the outset of the 2020 season, a certain segment of the baseball intelligentsia was all agog about Jesus Luzardo. He was clearly a Rookie of the Year contender and perhaps a sleeper for the Cy Young Award.

Not so much, as it turned out. Luzardo wasn't bad, per se, but nor was he great as he pitched to a 4.12 ERA in 59 innings. He indeed got hit pretty hard, yielding exit velocity in the 38th percentile.

Even still, left-handers who can sit at 95.5 mph and climb as high as 99 mph don't grow on trees. Likewise, Luzardo's breaking ball and changeup also have plus potential.

In short, Luzardo should only get better after dabbling in mediocrity as a rookie. 

2021 Age: 24

The 2020 season was the latest in a line of disappointments that's getting to be too long, but at least the Philadelphia Phillies got to watch Alec Bohm come into his own.

The Phillies installed Bohm at third base on August 13, and he never looked back. In 44 games, he hit .338 and cranked out 11 doubles and four home runs.

What's more, Bohm's peripheral metrics don't warn of an imminent fall from grace. He did pretty much everything well, including hit the ball hard. His hard-hit rate was in the 84th percentile.

Because he's bound to add more bulk to his 6'5" frame, that number and Bohm's overall power output should only get better going forward.

2021 Age: 24

Elsewhere in Pennsylvania, the Pittsburgh Pirates have a good young third baseman of their own.

As he was coming up through the minors, Ke'Bryan Hayes was generally regarded as a defender first and a hitter second. As such, it wasn't unexpected when he posted four defensive runs saved and three outs above average despite playing only 24 games.

The surprising part was how much Hayes contributed at the plate. He hit .376 with 14 extra-base hits, including five home runs. In light of his low strikeout total (20) and high exit velocity (92.8 mph), that performance is oddly believable.

In other words, the Pirates have a potential superstar at the hot corner.

2021 Age: 22

Sure, we could have gone with Fernando Tatis Jr. But given that he's already been a Rookie of the Year and MVP contender in two seasons with the San Diego Padres, that would have been too easy.

Besides, we quite like what Adrian Morejon has to offer.

It's less than ideal that he served up seven home runs in only 19.1 innings last season. Yet he still pitched to a not-terrible 4.66 ERA, and with a 25-to-4 strikeout-to-walk ratio.

That speaks to the control Morejon has of his stuff, which includes a fastball that averages 96.6 mph and a slider and curveball that have dynamic movement. So whether it's in relief or as a starter, he can be a dangerous weapon if he gets over his home run woes.

2021 Age: 24

Perhaps the best word to describe the San Francisco Giants roster is "old." Most of their key players are in their 30s.

That includes longtime catcher Buster Posey, but he's ticketed for a future in which he plays more first base in deference to Joey Bart.

The Giants nabbed Bart with the No. 2 pick in the 2018 draft, and he had people clambering for his call-up just a year later. After it finally happened August 20, the results were generally unspectacular. Bart played in 33 games and managed only a .609 OPS.

He did so, however, with sturdy numbers in the hard-hit rate (48.4 percent) and exit velocity (89.0 mph) columns. With more of that, he can live up to his billing as a slugging catcher.

2021 Age: 25

With respect to 25-year-old center fielder Kyle Lewis, picking him for this space would have been too easy given that he just won the American League Rookie of the Year Award.

It's a good thing Justus Sheffield was no slouch in his last season.

Sheffield took 10 turns in the Seattle Mariners rotation and ended up with a 3.58 ERA in 55.1 innings. The catch should be that he struck out only 48 batters, but his style of pitching is such that this isn't a deal-breaker.

Sheffield has been aiming more for ground balls ever since he ditched his four-seamer in favor of a sinker. As long as he keeps his ground-ball rate above 50, there will be no going back.

2021 Age: 22

The St. Louis Cardinals came into 2020 hoping Dylan Carlson would catch fire, and he did.

Eventually.

The Cardinals called Carlson up August 15, but he struggled so badly out of the gate that he was optioned back to the club's alternate training site September 8. Upon returning September 18, though, he went 10-for-35 with seven extra-base hits over his last 11 starts.

That was more in line with Carlson's stellar performance—i.e., a .914 OPS with 26 homers—in the minors in 2019. The Cardinals can thus hope he picks up where he left off come next season.

2021 Age: 25

The Tampa Bay Rays are a bit of an oddity. They have plenty of 20-something stars, but relatively few of them will be 25 or younger next season.

Among the exceptions is Willy Adames, who keeps finding new ways to inch toward stardom at shortstop.

In 2020, Adames tried a way that involved hitting the ball very hard. He averaged 88.8 mph on his batted balls and ended up with an ample 40.5 hard-hit percentage. 

From here, Adames must lower a strikeout rate that ballooned to 36.1 percent and get back on track defensively after yielding minus-six outs above average. It may bode well that he's previously performed capably in both arenas.

2021 Age: 22

The Texas Rangers may have little choice but to rebuild after finishing an AL-worst 22-38 in 2020, but they may already have their center fielder of the future.

Mind you, Leody Taveras was hardly perfect last season. In 33 games, he hit just .227 with a .703 OPS and also finished with zero outs above average on defense.

But if nothing else, Taveras should improve in the field. Though his results didn't show it, his glove work combined elite speed (96th percentile) and a quick first step (81st percentile).

Taveras must work on making contact after striking out 43 times in only 134 trips to the plate. He did, however, tease an enticing power-speed combination with 11 extra-base hits and eight steals in eight attempts.

2021 Age: 23

The Toronto Blue Jays are seemingly nothing but up-and-coming 20-somethings, yet you want us to pick only one?

Very well, then. We'll take Bo Bichette.

With all respect to Vladimir Guerrero Jr. and the underrated Cavan Biggio, Bichette is simply the closest to stardom. After just 75 games, all he's done is hit .307 with an .896 OPS, 16 homers and eight steals, which are stellar offensive numbers by shortstop standards.

Bichette's defensive quality is tougher to pin down. But not unlike, say, Xander Bogaerts, his bat could keep him at short even if his glove is never quite worthy of the position.

2021 Age: 21

Even if Juan Soto hasn't been an All-Star yet, he's a batting champion, a Rookie of the Year runner-up and a World Series hero. That's more than enough for the "star" label.

Even if he never reaches those heights, the Washington Nationals can have high hopes for Luis Garcia.

Despite his youth and his lack of experience above the Double-A level, the Nats called Garcia up on August 14. He homered three days later and hit a solid .276 in 40 games.

Garcia's exit velocity (83.5 mph) and defense (minus-four outs above average) indicate he still needs a lot of work. However, to perform so well in the majors despite being so young and relatively inexperienced points to his upside.

Stats courtesy of Baseball Reference, FanGraphs and Baseball Savant.