Ahead of Sunday’s highly-anticipated clash at Stamford Bridge, ESPNSTAR.com takes a look at the areas in which the game could be won and lost.

In their previous meeting earlier this season at Old Trafford, a surprisingly meek Chelsea outfit found themselves 3-0 down at half-time after goals from Chris Smalling, Nani and Wayne Rooney put Manchester United firmly in control.

Nonetheless, the Blues came out for the second 45 will all guns blazing and pulled one back immediately through Fernando Torres. However, the Spaniard turned from hero to villain seven minutes from time as he inexplicably fired a shot wide with the goal gaping, after he had expertly rounded United goalkeeper David de Gea.

Ahead of what is likely to be an intriguing encounter, we take a look at the potentially key match-ups.

A tale of two keepers

It's generally accepted that Chelsea have been inconsistent all season long, illustrated by their position in the Barclays Premier League table, where they are currently fourth,15 points behind City.

However, the one area that has been the least of Blues manager Andre Villas-Boas' concerns has been in goal, where Petr Cech remains one of the best stoppers in the league, as he has been throughout his time in England.

And while he arrived with similar expectations earlier in the summer, the same cannot be said for United's David de Gea, who was been erratic at best since joining from Atletico Madrid. The 21-year-old is capable of pulling off brilliant saves, yet seems to be incapable of handling the basics, letting tame efforts slip under his body and flapping at almost every ball in the air.

The good news for De Gea is that Chelsea aren't the most physical side in the league, especially with Didier Drogba on African Cup of Nations duty with Ivory Coast. With John Terry also ruled out through injury, Chelsea are less likely to threaten from set-pieces, which would hand United a huge advantage.

De Gea is still under a slight injury cloud after missing United's midweek game against Stoke, but despite a clean sheet by rookie custodian Ben Amos in that match, expect Sir Alex Ferguson to give the Spaniard to nod if he's fit.

The flying Sturridge vs the 'steady' Evra

Torres' goalscoring woes this season have been slightly masked by the fact that Chelsea have not struggled to find the back of the net, and for that, plenty of credit has to be given to Daniel Sturridge.

The ex-Manchester City man has stepped up to the plate brilliantly this term, and has already bagged ten goals in 20 appearances in all competition. Despite being predominantly left-footed, Sturridge does his best work on the right wing, where he excels at cutting inside his opponent before unleashing ferocious efforts goalwards. And far from being a one-dimensional player, the England international is also capable of going back on the outside before whipping in crosses on his right, meaning opposition defenders will always be kept guessing.

On Sunday, he is likely to come up against a player once regarded as the best left-back in the country - Patrice Evra. Thrice named in the PFA Premier League Team of the Year, the Frenchman has looked a shadow of his former self in recent matches, especially in the FA Cup 4th round clash against Liverpool, where he was culpable for letting Dirk Kuyt sneak in to score the winner.

A notable flaw in Evra's game is that he has always struggled against quick and tricky wingers, with Theo Walcott and Aaron Lennon being two major antagonists in the past. Against a similar opponent in Sturridge, one expects United's stand-in captain to be in for a long afternoon on Sunday.

Where United hurt Chelsea last time out

When United raced to a 3-0 lead inside 45 minutes in their last encounter at Old Trafford, Chelsea seemed to struggle with the pace and width of United's attack. The Red Devils regularly switched play from right to left, leaving Terry and company in shambles at the back.

Nani was the most dangerous player on the park that day, and despite having been out of action since the 2-1 win over Arsenal in January, the Portuguese is back in action and Ferguson has already hinted he could feature.

The greater concern for Villas-Boas is not who could threaten for United, but who he has available that could hold firm at the back. With Terry ruled out and Ashley Cole suspended after seeing red in Tuesday's 1-1 draw with Swansea, Chelsea could potentially field a back four that are unfamiliar with one another.

The most likely scenario would see Jose Bosingwa cover for Cole on the left, Branislav Ivanovic play on the right, with David Luiz partnering January signing Gary Cahill in the heart of defence. However, Luiz's defending is far from convincing and he has a poor record against United, while Cahill is yet to make his debut for the Blues. Given the ex-Bolton man's international credentials, starting him might seem the right move yet considering he has never played alongside Luiz, it remains a gamble.

Add to that the fact that Danny Welbeck has been on fire this season, while Javier Hernandez and Dimitar Berbatov both scored against Stoke on Tuesday. And lest we forget, rumour has it that Rooney will be fit to start.

A battle of wits between two veterans

In the immediate aftermath of last September's match at Old Trafford, one would have laughed at suggestions that either one of the Premier League's two greatest schemers - Paul Scholes and Frank Lampard - would ever take part in a United vs Chelsea clash again. For one, Scholes was long retired, while Lampard, having been unceremoniously hauled off by Villas-Boas at halftime, was said to have reached the end of his Chelsea career.

Five months on, both players could once again prove pivotal on Sunday. Scholes, having returned from retirement, has arguably been United's second-best player over the last month, behind only Antonio Valencia. Lampard, on the other hand, still has to take his turn on the bench every other game, but having been rested against Swansea, the 33-year-old looks set to take his place in Chelsea's starting XI on Sunday.

While both are expected to pull the strings for their respective teams, the pressure on them is slightly lessened due to their more-than-capable sidekicks.

Scholes will do battle alongside longtime partner Michael Carrick, and while the latter lacks the creative spark, he is excellent at winning possession with his well-timed tackles and telepathic interceptions. Given his penchant for playing the short pass, he could just be the man who loads the bullet in the gun that Scholes will fire.

To say Juan Mata will be Lampard's sidekick on Sunday would be an insult to the Spaniard, who has in fact been Chelsea's playmaker-in-chief for much of this season. What Villas-Boas will be looking for them to do, however, is to share the workload and offer two different threats to the United defence.

Despite his increasing years, Lampard is still the best when it comes to picking out a defence-splitting pass, while Mata thrives on gliding past defenders before sliding in team-mates with slide-rule balls. If both of them manage to work in tandem, the United back four could be under severe pressure.