England vs. Wales: 5 Key Battles That Will Shape 2016 RBS 6 Nations Clash

England's hopes of a 2016 RBS Six Nations Grand Slam lie on the line this Saturday when they welcome fierce rivals Wales back to Twickenham in a showdown that will most likely decide this year's champion.

It's been almost six months since the Red Rose suffered a 28-25 home defeat to the Welsh at the 2015 World Cup, but coach Eddie Jones is at the helm now and hoping for a much-altered course of action, not to mention result.

Wales coach Warren Gatland, on the other hand, is looking to lead Wales to back-to-back Twickenham victories over England for the first time since 1978, and this squad has already proved capable of the feat.

We break down the biggest battles ready to unfold in the English capital this week as undefeated duo England and Wales search to keep their 2016 RBS Six Nations title hopes intact.

Jonathan Joseph against Jonathan Davies was the centre battle every fan wanted but didn't get to see at last year's World Cup, due to the fact both were absent through injury back in September.

Fast-forward to the present, and it's easy to see why the masses were baying for this particular head-to-head, with England centre Joseph currently leading the try count (three), while Davies has also enjoyed talismanic form.

It is worth noting that while Davies is yet to score in this year's tournament, all three of Joseph's tries came in in the 40-9 humiliation of Italy; otherwise, England have largely leaned on their back three to score.

A titanic "Duel of the Jonathans" is ready to unfold at English headquarters as two of Europe's most effective ball-carrying centres prepare to clash in a meaty battle that will also put their defensive nous to the test.

Rarely does the rugby world get to see two No. 8 powerhouses in such stellar form front up against one another than in the collision Billy Vunipola and Taulupe Faletau will exhibit at Twickenham in Round 4.

Wales captain Sam Warburton said this week that the matchup could be a potential game-decider, and if either No. 8 gets a head of steam, it will make things terrifically difficult for their opposition, per BBC Sport:

If either has a very good game it's going to go a long way towards that team winning the match. 

Toby's [Faletau] one of the best players I've played with.

He's gifted in the sense that he can do everything. I don't think anyone could find an attribute that he can't do on the field. 

I think that's going to be a massive battle between those two number eights.

Billy's been a class act for the past three matches and I've always been impressed with him when I've watched him for Saracens and he's always been one of England's go-to players.

Vunipola in particular has been a phenomenal carrying force for England, and his 207 metres with ball in hand means he leads the tournament in carrying, while Faletau has mustered less than a quarter of that total (46), per BBC Sport's stat comparison.

But while England have thrived in attack—the added advantage being they've already faced Wooden Spoon favourites Italy—Wales' No. 8 has excelled in defence, making 54 tackles in three outings, while cousin Vunipola has only half that (27).

The family tie between these two brutes adds that extra bit of spice to any match in which they both happen to feature, and their respective performances could underpin any attacking momentum either team gains.

Jones' decision to run with Owen Farrell at inside centre has given George Ford a new lease to operate as England's first-choice No. 10, and it's worked to good effect—so far at least.

Wales have no such dilemma in electing their top fly-half, and Dan Biggar has pushed Wales on with 26 points from the tee; only Farrell (33) and Scotland captain Greig Laidlaw (41) have more to their name.

However, it may not be a direct duel between fly-halves that decides Saturday's tie after Welsh centre Jamie Roberts spoke of on his intent to target the slighter frame of Ford in the hopes of rattling his nerves, per the Press Association (h/t Eurosport):

George Ford is probably playing his best rugby at the moment, certainly in attack. 

He attacks the line flat and creates problems for the opposition. He is someone we have to be wary of this week.

He is one of the smaller men, there is no doubt about that, and we have got some big backs. So, as Warren said, we won't disappoint in that respect. That's rugby.

Biggar himself is no small factor in that equation, standing at 6'2" and 90 kilograms, and the Ospreys fly-half showed his gung ho stance at its best during last September's triumph at Twickenham.

Ford played just a 10-minute cameo on that occasion, and perhaps it was no coincidence Biggar helped craft a match-defining Gareth Davies try just a minute after the Bath man's introduction last time these two sides met.

They'll battle from the first whistle this time around, though, and Ford will have his opportunity to prove Roberts wrong, needing his wits about him to scupper the assault of a physical Welsh line.

A member of the new English dynasty will look to show one of Europe's old-timers that the emerging generation is here to stay on Saturday as Maro Itoje undergoes the test of Wales veteran Alun Wyn Jones.

Itoje earned his England bow off the bench against Italy before making his full debut in the 21-10 win over Ireland last time out, but Jones will present the Saracens star's biggest direct challenge yet.

That goes for the physical task as well as the metaphorical, and ex-England international Tom May recently told the official England Rugby website of the examination Jones will present his young counterpart:

It’s very difficult for second row forwards to stand out, but no matter what game he plays in, he stands out as an unbelievable player. 

He is a big guy, he carries well, he leads from the front for Wales and I think that’s what is most important. He is a real talisman for them and is incredibly fit.

The amount of work he gets through is unbelievable and for someone who is on 103 caps, including the British & Irish Lions Test matches, he is up there with one of the best second-row forwards who would have played the game.

In terms of someone England need to pay attention to, within the Welsh pack he is one of guys that will be leading and driving them forward and if they can take him off his game slightly, which is not very easy, then they would have done a pretty good job.

Itoje's own work rate was evidenced by the fact he made 16 tackles against Ireland—the most managed by any England player—and there are certainly worse ways for one to make their first Test start.

Jones has the advantage in experience heading into these occasions, but he faces one of the most exciting, athletic lock figures in Europe right now, while both players' influence at the set piece will also be key.

Many felt Jack Nowell should have garnered more opportunities at the World Cup than he did, and the Exeter Chiefs utility is strutting his stuff now after being handed a chance under Jones.

Alex Cuthbert is also a man living on renewed chances for the time being, having ridden through a patch of torrid 2015 form and now seeking to rediscover the attacking strain that once made him such an international threat.

England's expansion under Jones has been evident, and it speaks volumes that just one of their nine tries scored thus far in the tournament is attributed to a forward (George Kruis vs. Scotland).

Wales have a similar ratio themselves, with Faletau the only forward responsible for scoring in their five-try haul, but one could claim Gatland's side have found it that much more difficult to get the ball wide.

Taking style and tactics out of the occasion, it will be extremely interesting to see how 5'10" Nowell fares against the 6'6" frame of Cuthbert and how frequently Wales seek to exert the latter's height advantage in their kicking game.

All statistics come courtesy of ESPN Scrum.