The defeat leaves the Gunners 12 points away from the Premier League leaders with 14 games to go.
Cesc Fabregas has made six assists in the Premier League this season.
Wilshere is on loan at Bournemouth while Arsenal have a midfield crisis.
Ramsey picked up the injury during Arsenal's loss to Watford.
Mbappe broke Thierry Henry's record to become the youngest goal scorer at Monaco.
Mourinho criticised officials again after United slumped to a 0-0 draw with Hull City.
Aaron Ramsey is expected to be ruled out again with calf injury.
Wenger watched Arsenal's defeat to Watford from the stands as he serves his four-match touchline ban.
Former Gunners striker accepts decision to limit signing to one in January transfer window.
Wenger will not be on the touchline for the next 3 games.
Akpom will spend the rest of the season at Brighton after failing to break into the Arsenal first-team.
Arsene Wenger has no plans to make any late January signings but two players could leave.
Arsenal lost 4-0 on their last visit to the St Mary's.
Sanchez has 18 months left on his contract at Arsenal.
Arsenal are currently second in the Premier League, 8 points behind Chelsea.
Xhaka is banned for four matches after picking up his second straight red of the season against Burnley.
The French boss also charged £25,000 for incidents of improper conduct and misconduct against Burnley.
The 21-year-old has scored seven goals in a struggling Werder Bremen side this season.
Wenger is awaiting the verdict of the FA charge following his tussle with the fourth official last weekend.
Arsenal are currently second in the league behind Chelsea.
Akpom has played just 83 minutes of first-team football for Arsenal this season.
Arsenal have only two available midfielders at the moment.