The selection or omission of Torres
There has been much talk of this, and no wonder why, amid rumours Chelsea manager Carlo Ancelotti is obligated by owner Roman Abramovich to select January acquisition Fernando Torres - a catch-22 situation for the Italian? The floodgates have so far failed to open for the £50million signing from Liverpool after 63 minutes against Tottenham Hotspur produced no second goal following the breaking of Torres' goalscoring duck versus West Ham. Common consensus seems to be that the Blues will have a stronger chance of victory at Old Trafford should they start with Didier Drogba in a solo striking role. In seasons gone by, Torres has given United's backline a rough ride, but in five appearances, for both Chelsea and Liverpool, versus the Red Devils this season the Spain international has failed to score. Drogba, meanwhile, netted in defeat after coming off the bench at United in the Champions League last month.
The centre of the park
Yes, you knew this already, but nonetheless this matter of the game being won and lost in midfield needs to be explored further. United's slump last weekend at Arsenal that blew open the title race largely hinged on their failings in the midfield battle. The partnership of Michael Carrick and Anderson proved a weak one as a youthful Gunners trio marshalled this area. Indeed, a view of that game's post-match statistics reveals the visitors lost out to their North London hosts on possession, passing success, number of passes made and territorial advantage. It is anticipated that Ryan Giggs will return to the starting line-up, the Welshman hoping to have a similar impact as he did in the two recent Champions League meetings. For Chelsea, meanwhile, the importance of their holding man cannot be underestimated as John Obi Mikel aims to replicate Arsenal midfielder Alex Song's successful job last weekend of nullifying the threat of Wayne Rooney.
The Old Trafford influence
United's home record this campaign has been near perfection. Indeed, Sir Alex Ferguson's men have dropped just two points on their own turf in the league this season. An even more eye-watering statistic is that no opposition player has scored a first-half goal at Old Trafford in the Premier League since Joe Cole did in this fixture last April - good heavens. So good has the table-toppers' points return been at home this term that two wins from their remaining matches at Old Trafford would match the record haul of 55 points set by none other than Jose Mourinho as Chelsea manager in the 2005/06 season.
The psychological factor
"The results against them in the Champions League were very good. I think that gives us the psychological advantage," said Nani. Yes, while Chelsea have strung a run together of five successive league triumphs, their two European stutters versus their rivals United have deflated that swelling balloon of confidence. However, it is a rare thing for United's own mental strength to be under scrutiny. Chelsea will take great heart from the previously-thought-impossible scenario that they are even in this position come May. Chelsea had fallen back to fifth and nine points behind the Red Devils, only for a combination of their resurgence and an unusual United wobble to present them with an opportunity of going top on goal difference with two matches to play. Now, talk of a Newcastle United-esque capitulation is making the pages in newspapers. On record, the Red Devils boast the highest May points return in the Premier League, but, despite Giggs stating: "We have not thought about losing a big lead", one cannot help but feel that a peculiar emotion for a United player called 'doubt' must lurk in the depths of players' minds.
The man in black
Let us talk facts: referee Howard Webb has awarded penalties to United in three of the last four competitive games he has officiated at Old Trafford. Also, Ferguson's charges have won the last seven Premier League matches at the Theatre of Dreams that Webb has officiated. Now the conjecture: Ferguson has wasted little time in ramping up the pressure on Webb ahead of Sunday's showdown. He claims that Chelsea benefited from "great decisions" in their 2-1 victory over Tottenham at Stamford Bridge last weekend. Yet, pressure is on all referees' shoulders this weekend, not just Webb's, following a number of controversial decisions in the previous round of Premier League fixtures. That said, Ryan Babel's Tweeted mock-up of Webb dressed in a Red Devils shirt remains burnt into one's memory.