Henrikh Mkhitaryan will miss Arsenal's Premier League game with Southampton on Sunday after picking up a knee knock against CSKA Moscow, while David Ospina faces up to three weeks out with an ankle problem.
Arsenal cruised to a 4-1 triumph over the Russian side at Emirates Stadium on Thursday, with Aaron Ramsey and Alexandre Lacazette getting two each.
The comfortable lead leaves them in the driving seat in the Europa League quarter-final tie, though a seemingly innocuous injury suffered by Mkhitaryan just after the hour could prove a blow, with Wenger expecting him to at least be out of Sunday's game.
"Mkhitaryan has a knee problem," Wenger told reporters in his post-match news conference.
"We don't know how bad it is. He will certainly be out for Sunday."
Ospina had been expected to start in goal for the visit of CSKA, but he was ruled out due to suffering an injury on Wednesday.
But the scan he had on the problem was "reassuring", according to Wenger.
"He just moved back to make a save and sprained his ankle. There was no contact," Wenger said.
"The scan today was reassuring. He will be out for two to three weeks. Yesterday [Wednesday] we were scared for a very serious injury, but today the scan was reassuring."
