Alexandre Lacazette's season is in danger of being over after the France striker suffered a hamstring injury against Fulham.
Club captain Pierre-Emerick Aubameyang is already out of the Arsenal squad after contracting malaria on a recent international trip to Gabon.
And Lacazette, who had scored four goals in the last two matches, pulled his jersey over his head in frustration as he limped off in the second half at the Emirates Stadium.
Arsenal face Unai Emery's Villareal in the first leg of the Europa League semi-finals on April 29.
“We will have to see - he felt his hamstring so we don't know,” said head coach Mikel Aretta.
“We will have the scans on Tuesday and see the extend of the injury. I don't know.
“I cannot tell you if it is going to be a week or five or six weeks. We are all disappointed because we know Laca was on form.
"We have to rotate players, we have players who didn't recover from the game on Thursday.
"That is the risk. You cannot change those players every game.”
Arteta, who made five changes to the team which won at Slavia Prague, has not won back-to-back Premier League matches since January to remain in ninth place – nine points off the Champions League places and six behind sixth-placed Liverpool
“That is the reason why we are where we are in the league. They are the game we have to win. When you don't do it, there are consequences in the league.”
“Absolutely we needed the win today. We need to win every game to give us a chance (to finish fourth).
"Mathematically it is still possible.”
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