Arsenal manager Arsene Wenger has confirmed that Henrikh Mkhitaryan will be out for at least two weeks with knee ligament damage.
The Armenia international was injured in Thursday's Europa League quarter-final first-leg win over CSKA Moscow.
A scan on Friday confirmed fears that Mkhitaryan will face a spell on the sidelines but Wenger expects his player to be back before the season is over.
"Mkhitaryan has medial knee ligament damage," the Frenchman told reporters after Sunday's 3-2 win over Southampton.
"He will miss [the next two weeks] for sure. He could still play at the end of the season."
Mkhitaryan is expected to be sidelined for Thursday's trip to CSKA, Newcastle United on Sunday and West Ham United the following weekend.