Games between Chelsea and Manchester United have had a rather big bearing on the Premier League for some time now, and Sunday's clash will be no different. It promises to be an enterprising game with both sides looking strong in attack, and slightly less so in defence.

The dynamic of the game will largely come down to Sir Alex Ferguson's formation choice. Against Braga midweek, the Scotsman elected to play United's rather unusual diamond formation, as he did against Newcastle and CFR Cluj before the international break. It's unusual to see United playing a system that essentially abandons wingers, considering the club's recent history (and ancient history) has been built upon a dedication to fleet-footed touchline play. "If it turns out as a consistent team selection from me, playing a diamond, it is revolutionary because we're going against our history," said Ferguson. So what would a diamond mean for this weekend's game?

The 'new' system

Simply, with four players down the centre of the park, it would allow United to dominate midfield, and most likely, possession. With Wayne Rooney at the tip supporting Robin Van Persie and one of Javier Hernandez or Danny Welbeck, it's a particularly fluid system, with Van Persie in particular drawn into wide left and right positions to create space for runners from midfield. Darren Fletcher played at the base midweek but it would more likely be Michael Carrick against Chelsea. Neither of those two players would be particularly comfortable playing as a nominal holding midfielder, but that's the benefit of the diamond system, as it provides two extra midfielders - generally termed carrielos - to provide support. Tom Cleverley would surely be one starter in this system, and his energy is crucial to dictating United's pressing game.

By packing the midfield, United would clog the zone in which Chelsea's band of three likes to operate. The full-backs would provide the width with no wide players playing in front of them, meaning the match would revolve around the battle down the full-back positions, where one would think Ashley Cole and Branislav Ivanovic would be able to overpower Rafael and Patrice Evra respectively. Ferguson has always sought to play with width against Chelsea, and the diamond wouldn't provide this naturally.

The 'regular' system

The other option is, of course, the tried and tested 4-4-1-1/4-2-2 formation, where United would play with a solid bank of four in midfield and, in the enforced absence of Shinji Kagawa, Rooney playing off Van Persie up front. Considering that Chelsea's fullbacks lack protection from the wide attackers and are vulnerable in one-on-one situations, this appears to be a system more suited to exploiting Chelsea's weaknesses, but the trade-off is that with just two players in the midfield zone, United run the enormous risk of being engulfed by the fluid interchange of Juan Mata, Eden Hazard and Oscar. That trio seems set to reprise their role as the instigators of Chelsea's creativity behind Fernando Torres. The Spaniard has been much maligned for his performance mid-week but his intelligent movement off the ball was widely ignored: running diagonally across the centre backs, he opened up space for Eden Hazard to move into dangerous, central playmaking zones.

That's a move not entirely dissimilar to what Gareth Bale, Jan Vertonghen and Jermain Defoe employed to score Tottenham's first and second goals in that famous 3-2 win back in October. Rio Ferdinand is particularly vulnerable to players running directly at him towards goal - the central defender backs off and tries to funnel the player wide, but simply allows too much space to open up in the penalty area and has thus been exploited not only by the aforementioned but also by Michael Kightly, of Stoke. Yes. Michael Kightly.

Chelsea approach



So there you have it. Two systems available to Ferguson, both with widely apparent strengths and weaknesses. It's anyone's guess what he might do (although I'm tending to think he'll opt for the 4-4-2 and look to pin Ashley Cole deep with Antonio Valencia, since he's been so concerned about the fullbacks attacking play so often in the past) and it's worth remembering that Di Matteo's tactics will also play a part.

The Italian might even pull out a surprise with Ryan Bertrand playing down the left flank: it'd be unexpected, but don't count it out. If that doesn't happen (in all likelihood, it's an elementary decision between Oscar or Bertrand - Hazard and Mata are virtually guaranteed starts), Oscar will be instructed to disrupt Carrick/Scholes's passing from deep in a role similar to that of the one against Arsenal, while David Luiz and Gary Cahill will be aware of the devastating movement of the two forwards. It's paramount that the centre-backs aren't dragged across the pitch chasing shadows - looking at you, David - else United's dynamic midfield (Tom Cleverley in particular) will be able to take advantage.

Set pieces

Set pieces will also be important: Chelsea haven't looked too flash defending them and the clever movement of Van Persie in the area will require a similarly-mobile marker. David De Gea is perhaps unfairly cast as a goalkeeper 'not cut up for the rigors of the physical Premier League,' but he is certainly vulnerable to corners where he is required to move off his line. With that in mind, I'd like to see Juan Mata taking out-swingers from the left, looking for either a near post run from Torres or Ivanovic around the six-yard area.

Conclusion

Both sides have breathtaking attacks, and slightly less admirable defenses. That means this will almost certainly be an open game, regardless of formation. Combine that with some high stakes, and who knows what on earth could happen.