The Armenian playmaker started for the Gunners in their 4-1 win over CSKA Moscow in the first leg of their Europa League quarter-final clash at The Emirates in midweek.
However, the 29-year-old had to be replaced in the second half after sustaining a knee problem.
Speaking at his post-match news conference at The Emirates on Thursday night, Wenger confirmed that Mkhitaryan was set to undergo a scan on Friday morning and said that the playmaker would not be fit for the visit of Southampton to Arsenal on Sunday in the Premier League.
Wenger said: “He has a knee problem, we don’t know how bad it is, we have to assess it tomorrow morning. He will certainly be out for Sunday.”
Mkhitaryan has been settling into life at The Emirates after having signed for the Gunners from Manchester United in the January transfer window as part of the deal which saw Alexis Sanchez head to Old Trafford.
He has scored two goals and made five assists for the north London side since moving to Arsenal from the Red Devils at the turn of the year.
Arsenal will take on CKSA Moscow in the return leg of their Europa League quarter-final tie on Thursday night next week as they bid to make it through to the semi-finals.
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