Old Trafford has traditionally been a pretty tough place for Arsenal, where, prior to this season's FA Cup win, they hadn't beaten Manchester United since Emmanuel Adebayor scored an 86th minute winner back in 2006 (fortunately, that didn't stop the Red Devils going on to win the title by six points).
United will hope their home ground can once again become the fortress that the Gunners can't conquer when Arsène Wenger's side come to visit on Sunday, particularly with third place -- and the avoidance of a nervy Champions League qualifying round -- still just about up for grabs.
United will be without Michael Carrick for the rest of the season, but rather more tragic is that it looks like they'll be without Rafael for the rest of eternity. Continuing the theme, Wayne Rooney could be fit to play despite being forced off last week, though Luke Shaw, Marcos Rojo and Robin van Persie are all likely to be involved in some capacity.
Arsenal are unlikely to throw the recently-recovered Mikel Arteta and Alex Oxlade-Chamberlain in at the deep end in this match, though Danny Welbeck and Mathieu Debuchy could be available.
This season Wenger has shown glimpses of finally moving beyond the admirable-but-slightly-naïve style of pretty possession football and very little defending, most notably manifesting itself with a gritty win away at Manchester City in January. That is almost certainly the right way for the Gunners to go, given their rather lightweight midfield and the quick attacking threat of Alexis Sánchez in particular, but there's very little way of knowing which Gunners side are going to turn up at Old Trafford on Sunday.
What we can take a guess at is personnel, and the one-on-one battles that could be the key to this match. It will likely be Antonio Valencia who will be tasked with keeping Sánchez quiet, which is a slightly alarming prospect. However, if there's one thing Ecuadorian Tony can do, it's run, while his complete unwillingness to do anything at all in the final third means it's probably preferable to have him marking Sánchez than Luke Shaw, whose recent attacking ventures have shown some promise.
Young defensive midfielder Francis Coquelin has amazed Arsenal fans this season with his midfield tenacity in the same way that United fans would be left gobsmacked by signing a defensive midfielder who could both pass and tackle. It is what they've been lacking for such a startlingly long time that it's at once surprising and not at all surprising that they finally have it. However, while Coquelin is strong in the tackle, he's not particularly tall: at 5'10" he's one of their tallest midfielders, but bearing in mind they're officially the shortest team in the Premier League (hey, another trophy for Arsène!), that won't be helpful up against Marouane Fellaini.
Providing Daley Blind can do a job on Mesut Özil, the key technical battle in the middle of the field could well be between Ander Herrera and Santi Cazorla: two players who thrive on finding space with darting runs from deep. It could well be that matchup that decides the flow of this game. With Olivier Giroud up front pretty good at bringing long balls down and holding play up in the opponent's half, he's probably not going to win the Gunners this game alone.