Top Prospects Who Will Play Critical Role in 2019 MLB Playoff Races

The time has come for teams across Major League Baseball to follow the league's official advice: Let the kids play.

As a result of roster expansion, there will be prospects aplenty either debuting or returning to the majors in September. Rather than focus on all of them, we've rounded up a list of the best of the best who figure to play roles in the American League and National League pennant races.

These are guys who not only play for contenders but who are going to get a chance to contribute in a significant capacity. We were mainly interested in top-100 prospects, so we've highlighted nine from MLB.com's rankings who could make an impact this month.

But first, we'll begin with some honorable mentions.

Adbert Alzolay, RHP, Chicago Cubs

As they seek to win a hard-fought race for the NL Central, the Chicago Cubs will likely call up Adbert Alzolay at some point. The fastball-curveball combination behind his rate of 12.5 strikeouts per nine innings at Triple-A should serve him well in a bullpen role.

Bobby Dalbec, 1B/3B, Boston Red Sox

The Boston Red Sox don't seem to be in a hurry to call up Bobby Dalbec, yet he's a candidate to get some on-the-job training amid the team's wild-card pursuit. He's clubbed 27 home runs in the minors this year, including seven in only 29 games at Triple-A.

Jon Duplantier, RHP, Arizona Diamondbacks

Unlike Dalbec, Jon Duplantier has already made his major league debut. He's also already been recalled by the Arizona Diamondbacks, who might continue to sneak up the ranks in the NL wild-card race if he puts his fastball-curveball-slider mix to good use in the bullpen.

Junior Fernandez, RHP, St. Louis Cardinals

Though catcher Andrew Knizner, outfielder Randy Arozarena and left-hander Genesis Cabrera also deserve shoutouts, Junior Fernandez takes the cake as the St. Louis Cardinals' most intriguing September call-up. His fastball, which averaged 96.7 mph in his first MLB stint, should give their bullpen a boost.

Nate Lowe, 1B/DH, Tampa Bay Rays

Nate Lowe has hit everywhere he's played this year, including the majors to the tune of a .921 OPS and six homers in 31 games. If there's more where that came from, the Tampa Bay Rays will keep pushing the Oakland Athletics for the AL's second wild card.

MLB.com Rank: No. 62

As Jack Curry of the YES Network was first to report, Deivi Garcia did not make the cut for the New York Yankees' first wave of September call-ups.

That doesn't mean he won't get the call at all, however. It may only be because the Yankees don't want to rush the 20-year-old any more than they have to.

"We've got to finish his development off," general manager Brian Cashman said of Garcia on WFAN on August 2, according to Brendan Kuty of NJ.com. "If he does help here this year, it'll be out of the bullpen."

The Yankees don't need Garcia's help to wrap up their first AL East title since 2012, but they need all the help they can get to hold off the Houston Astros in the race for the American League's top record.

To this end, Garcia could indeed have a part to play. Though the 5'9", 163-pounder still needs to refine his control for a future starting role, his stuff is good-to-go for relief work. He has an outstanding fastball-curveball combination that's allowed him to rack up 13.5 strikeouts per nine innings in the minors this year.

MLB.com Rank: No. 54

The Minnesota Twins can certainly hit home runs, but their effort to outlast the Cleveland Indians in the AL Central race could use more pitching.

This is where Brusdar Graterol comes in.

The 21-year-old was part of Minnesota's first wave of call-ups Sunday, which followed a minor league season that was equal parts frustrating and dominant. Graterol missed time with a shoulder impingement, yet he pitched to a 1.92 ERA over 61 innings when healthy.

Though Graterol's future is in the Twins' starting rotation, the club is undoubtedly salivating over what he could bring to the bullpen down the stretch and into the postseason. Specifically, his fastball sits in the high 90s and has been clocked as fast as 103.8 mph.

According to FanGraphs wins above replacement, the Twins bullpen is already the AL's best since the All-Star break. With Graterol now aboard, it could turn into a not-so-secret weapon for October.

MLB.com Rank: No. 43

The Oakland Athletics have had as much trouble as anyone getting production out of the catcher's spot this season. According to Baseball Reference, their backstops have combined for a total of 0.2 WAR.

It's a wonder they didn't call up Sean Murphy sooner than Sunday.

The knee troubles that Murphy, 24, has experienced haven't been good for his timeline. His offensive production, on the other hand, hasn't suffered in the slightest. In 31 games at Triple-A, he hit .308 with a 1.011 OPS and 10 home runs.

Yet it's Murphy's defense that's typically earned him glowing reviews from scouts. The 2016 third-rounder's defensive skill set includes elite arm strength and strong receiving and blocking abilities.

"His defensive skills are off the chart," A's farm director Keith Lieppman told Casey Tefertiller of Baseball America in April. "He was a real steal at where we were able to get him."

Now that Murphy is with the A's, a lineup that already features both good bats and good gloves could get that much better.

MLB.com Rank: No. 35

Though the Atlanta Braves have one of the best farm systems in MLB, they didn't include any of their big-name prospects in their first expansion. Their time will come later.

If there's one among the bunch who could make a real difference, it's Kyle Wright.

This would seem like a flimsy conclusion based on how the 23-year-old has responded to major league exposure in the past. He was good but not great in four relief appearances in 2018. Earlier in 2019, he walked 13 and allowed 18 earned runs in four starts.

Yet Wright has little left to prove in the minors at this point, as he's pitched well with a 3.00 ERA, 49 strikeouts and 14 walks over his last seven appearances at Triple-A. 

Wright has four above-average pitches that he could put to work in the Braves rotation, possibly in place of Mike Foltynewicz. What's more likely, however, is that he'll get a chance to play up his outstanding fastball and curveball in a relief role.

Even in that capacity, he can help the Braves finish off a second straight NL East title.

MLB.com Rank: No. 20

In all honesty, it was a tough call whether to include Carter Kieboom on this list.

For one thing, the soon-to-be 22-year-old wasn't included in the Washington Nationals' initial roster expansion Sunday. For another, there may not be much playing time for him in an infield that has Anthony Rendon at third, Trea Turner at short and Asdrubal Cabrera and Brian Dozier at second.

Still, it's likely Kieboom will be seen at some point.

He's already made his major league debut, and the Nats might as well bring him back up after the Triple-A season is over. With Rendon, Cabrera and Dozier due for free agency, it's a good idea to give Kieboom as much experience as possible before he's needed for real next season.

In the meantime, he could make a difference in the Nats' wild-card pursuit as a spot starter and pinch hitter. The latter could prove to be a specialty, as his .305/.411/.496 batting line at Triple-A underscores just how talented he is with a bat in his hands.

MLB.com Rank: No. 18

Unlike Sean Murphy, Jesus Luzardo didn't get called up by the A's on Sunday. But as Susan Slusser of the San Francisco Chronicle indicated, that may only be because he started for Triple-A Las Vegas on Friday.

By all rights, the 21-year-old should have made his major league debut shortly after he wowed everyone in spring training. Alas, much of his season was derailed first by a rotator cuff strain and then by a lat strain.

When Luzardo has been on the mound, however, it's been business as usual. He pitched to a 2.51 ERA and a whopping 7.1 strikeout-to-walk ratio over 43 minor league innings. Altogether, he has a 2.53 ERA and 5.4 K/BB ratio over three seasons in the minors.

It helps that Luzardo has an excellent fastball and changeup and a pretty good curveball. What helps even more is that he can throw the ball where he wants better than most pitchers his age. 

A guy with these skills could bolster pretty much any rotation. He could especially bolster an A's rotation that's been on thin ice with a 4.09 ERA and MLB-low strikeout rate over the last two seasons.

MLB.com Rank: No. 14

Following a brief stay on the injured list with left shoulder fatigue, Brendan McKay returned to strike out eight batters with only one walk and one hit allowed in three innings for Triple-A Durham on Friday.

Next stop, Tampa Bay.

McKay, 23, has already made eight starts for the Rays with results that have been...well, mixed. His 5.55 ERA and eight home runs allowed jump off the page in a bad way, but he's also struck out 41 and walked only 12 in 35.2 innings.

The latter two figures highlight how McKay's stuff—namely his fastball, cutter and curveball—and control are ready for the majors. And with Blake Snell and Tyler Glasnow still on the injured list, the Rays need that skill set back in their rotation as soon as possible.

They might also have a use for McKay's bat as they seek to wrap up a wild-card spot. There hasn't been much thunder in his stick at the major league level yet, but he's mustered an .839 OPS at Triple-A this season.

MLB.com Rank: No. 12

Nothing is official as of Sunday. But according to Chandler Rome of the Houston Chronicle, Kyle Tucker will get the call to the Astros as soon as Monday.

If he played for virtually any other organization, the 22-year-old would have been in the majors a long time ago. Tucker finished 2018 with a .989 OPS, 24 homers and 20 stolen bases at Triple-A, and he stayed on that trajectory this season with a .909 OPS, 34 homers and 30 steals.

Trouble is, the Astros have George Springer, Michael Brantley and Josh Reddick locked in as regulars in their outfield, with Jake Marisnick standing by in reserve. Even in September, that'll be a tough nut for Tucker to crack.

Nonetheless, he should at least see action as a spot starter and pinch hitter. If Tucker seizes those opportunities, manager AJ Hinch might feel compelled to start playing him in right field over Reddick, who's having one of his worst seasons at the plate.

In any case, Tucker might just help the Astros overcome the Yankees for the AL's top seed.

MLB.com Rank: No. 9

As recently as last week, Los Angeles Dodgers manager Dave Roberts was telling reporters (including MLB.com's Ken Gurnick) that Gavin Lux would only be called up in an "apprenticeship" capacity.

Now, it seems that the team's thought process might be changing.

"We haven't decided if we're going to ... but he's really making a strong case for himself that he can help our club," Roberts said Saturday, according to Jorge Castillo of the Los Angeles Times.

The notion that Lux is making a "strong case for himself" is perhaps the understatement of the season. The 21-year-old has done nothing but hit over the last two seasons, and he's been roughly as hot as the core of the sun since he arrived at Triple-A. In 49 games, he's hit .392 with a 1.197 OPS and 13 homers.

Lux isn't going to supplant Corey Seager at shortstop, but there's an opening for him at second base in the wake of Max Muncy's broken wrist. The sooner he plants his flag at that position, the harder it will be for the Dodgers to take it away from him as they chase after an elusive World Series title.

Stats courtesy of Baseball Reference and FanGraphs