Arsene Wenger remains hopeful Henrikh Mkhitaryan will play again this season despite confirming the Armenia international suffered knee ligament damage against CSKA Moscow.
Wenger has already ruled the 29-year-old out of contention for the upcoming Premier League fixtures against Newcastle United and West Ham too, though he may yet be back for the run-in.
"He's got knee ligament damage," Wenger told the club's official website.
"He will not be available for Thursday and not for Newcastle and certainly not for the week after, when we play West Ham.
"I think he will miss these games for sure, but he could still play at the end of the season.”
Since coming over from the Red Devils, Mkhitaryan has scored two goals and added five assists in 12 appearances across all competitions.
In Mkhitaryan's absence, Danny Welbeck scored twice to help Arsenal extend their winning streak to six games in all competitions by seeing off Southampton at the Emirates Stadium.