Sagna limped off with an ankle injury at the Emirates
An injury picked up by Bacary Sagna added to Arsenal's misery after their title hopes suffered another blow with a 2-0 defeat at home to Aston Villa.
Manager Arsene Wenger said the French full-back will be out for a "few weeks" after injuring his ankle in the build-up to Villa's opening goal.
Gabriel Agbonlahor's strike sealed the win and the result leaves Arsenal nine points behind leaders Chelsea.
"The performance was not good," said an unhappy Wenger afterwards.
"Top-level performances are about consistency and at the moment we are not consistent enough."
The full extent of Sagna's injury is not yet known, but if Wenger's assessment is correct then he will not be fit to face Manchester City next Saturday.
Arsenal will also be without influential midfielder Cesc Fabregas for the trip to Eastlands after he was booked in the move that led to Ashley Young's first-half penalty miss and will be suspended.
Before then there is an international break and Wenger bemoaned the fact he will not have enough time with his squad to lift morale in the dressing room.
"Everyone is very down, it is a massive disappointment," added the Frenchman.
"Now I don't see them before Thursday or Friday, so I don't have a chance to pick them up."
Villa manager Martin O'Neill was delighted with his side's performance and hopes the result will give his players more confidence as they look to break into the top four.
After the win at the Emirates, Villa are level on points with Arsenal in fifth and O'Neill is now looking for consistency from his team.
"We were fearless," he said. "We have ability in the team, mark my words, it's getting them to believe they can keep going.
"The landmarks are to do with consistently performing. It was a great performance but it's a tough old season.
"But this will give the players great confidence, particularly in the way we missed the chances but didn't let that affect them."
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