If David Moyes is to emerge unscathed from a daunting trip to Stamford Bridge, Manchester United will have to be successful in key areas.
The centre of the park
United's central midfield has been a worry since Moyes' biggest concern was how to get the best out of Big Duncan Ferguson at Everton. Michael Carrick, Darren Fletcher, Tom Cleverley et al (sadly I just mean "and all the rest of them," not a new Brazilian superstar called Al) will be faced with twin challenges against Jose Mourinho's side.
On the one hand, they will need to provide defensive cover for centre-halves who will have their hands full trying to deal with the Premier League's best collection of creative attacking midfielders, ably supported by some combination of Ramires, David Luiz, John Obi Mikel and Frank Lampard.
On the other hand, they will have to ensure that United's front men and wingers do not become too isolated.
Praise has rightly been heaped on Adnan Januzaj and Shinji Kagawa for their creative contribution to last week's victory over Swansea, but Fletcher breaking forward in support created space, provided a range of passing options and gave Swansea's defenders something extra to think about. It seems unlikely that this will be a tactical battle United can win.
Much as in the derby at the Etihad earlier in the season, a two-man midfield could quickly find itself overwhelmed in terms of both quality and numbers. However, even with the numbers, quality could still be a significant issue. It is not clear how much defensive cover the inclusion of Cleverley would provide.
The final significant tactical option for Moyes in midfield would be a fit-again Phil Jones. Given his relative success in man-marking Cristiano Ronaldo in last season's Champions League clash and...erm...Marouane Fellaini in the league, assigning Jones to Eden Hazard would be an excellent option for Moyes.
United’s right flank
Antonio Valencia has had a lot of joy against Ashley Cole. When he was in the form which earned him United’s fans' player and players' player of the season trophies, Valencia looked like he had the certain beating of the Chelsea left-back.
Supported by Rafael and theoretically by whoever operates on the right side of United’s central midfield, whether Valencia can make a telling contribution in this game will be hugely dependent on form, confidence and Chelsea’s intent.
Mourinho’s approach asks less of their full-backs in terms of contributions to attacking play and it would not be hugely surprising to see Cole be less likely to bomb forward and more mindful of the counter-attack. In theory, United may have some joy down the wings against Chelsea’s narrower formation.
The space between Chelsea’s midfield and strikers—will Mata get a game?
Mourinho has such a wealth of attacking midfield talent that he often does without Chelsea’s best player last season, Juan Mata. Received wisdom suggests this is because Mata doesn't provide as much defensive cover as his colleagues.
Against United, that may not be so much of an issue. Not many United fans would feel comfortable with the ability of Moyes’ men to impose their will on Chelsea’s midfield, so Mourinho might be tempted to indulge in the luxury of including a player most teams would absolutely love to have in their first XI every week.
If Moyes does stick with an approximation of a 4-4-2, it will afford the three in Chelsea’s 4-2-3-1 a great deal of room to hurt United.