Arsenal manager Arsène Wenger has confirmed that Henrikh Mkhitaryan will have a medical assessment on Friday and will "certainly" miss the visit of Southampton on Sunday.
The 29-year-old was substituted in the 61st minute as Arsenal ran out 4-1 victors against CSKA Moscow in the Europa League on Thursday evening.
Mkhitaryan limped off with a knee injury after receiving treatment from physio Colin Lewin, and Wenger confirmed to the media after the game (via arsenal.com) that he will be assessed to determine the extent of his troubles.
Braces from Aaron Ramsey and Alexandre Lacazette saw the Gunners wrap up their victory against CSKA Moscow before half-time, meaning Arsenal now have one foot in the semi finals heading into the return leg in Russia.
However, Mkhitaryan's injury will have concerned Arsenal fans, as the Armenian has settled into the side well since his arrival from Manchester United in January.
Speaking after the game, Wenger said: “[Mkhitaryan] 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.”
Wenger also gave an update on the fitness of goalkeeper David Ospina, who sprained his ankle in training earlier this week.
"The scan today was reassuring, he will be out for two to three weeks," Wenger explained.
"Yesterday we were scared, it was a very serious injury but the scan was reassuring. Yes [he did it in training] - he just moved back from a shot and sprained his ankle, without any contact. It was just a bad movement."
Arsenal have now won five games in a row, scoring 15 goals in the process, but will be without Mkhitaryan when they welcome Southampton to the Emirates Stadium in the Premier League on Sunday.