Team news
Welbeck will try to shake off a hamstring knock picked up on international duty with England, but will face competition for his place from Olivier Giroud after the French striker returned to full training this week. Mesut Ozil remains out for Arsenal with a knee ligament injury, while defenders Laurent Koscielny and Mathieu Debuchy are both expected to be missing until mid-December. The key decision for Wenger will be whether or not to continue with Nacho Monreal as a makeshift centre-half following the Spaniard's disappointing showing in the 2-1 defeat to Swansea City last time out.
Manchester United's lengthy injury problems continued despite the international break, further destabilizing an already unbalanced squad. Daley Blind's knee injury is not as bad as first feared, but it is still expected to keep the Dutch midfielder out for the rest of 2014, leaving a gap in central midfield.
However, Michael Carrick is doubtful for this game after dropping out of England duty due to a groin problem. Star summer signings Angel di Maria and Radamel Falcao also face late fitness tests, while a host of defenders are on the treatment table. Rafael, Phil Jones (calf), Jonny Evans (ankle), Marcos Rojo (shoulder), and Luke Shaw (hamstring) are all doubts, while goalkeeper David de Gea has dislocated a finger.

Opta stats
Arsenal have dropped more points than any other team from winning positions in this season's Barclays Premier League (9). 
Juan Mata has scored four goals and set up two more in five starts against Arsenal in all competitions.
Wayne Rooney has scored the joint-most goals against Arsenal of any player in Premier League history (10 along with Robbie Fowler)
Only Burnley (8) have conceded more headed goals than Arsenal this season (6).
Alexis Sanchez has scored 12 goals in his last 14 matches for Arsenal in all competitions. 
Arsenal have won just four Premier League matches this season and those have come against teams currently in the bottom seven of the table.
Alexis Sanchez has scored the opening goal of the game more often than any other Premier League player this season (five times). 
Robin van Persie has scored in five of the last six meetings between Arsenal and Man Utd, in two games as a Gunner and three as a Red Devil. 
Danny Welbeck has scored in his last two appearances in this fixture, while playing for Man Utd.
Manchester United have lost just one of their last 14 matches against Arsenal in all competitions (W10 D3 L1).