Arsene Wenger is waiting to learn the extent of Laurent Koscielny's knee injury after the defender was forced to pull out of Arsenal's 3-0 win over Aston Villa.
Koscielny was pencilled in to start at the Emirates Stadium, but had been a late doubt prior to kick-off after waking up with pain in his knee.
The Frenchman was unable to shake off the problem during the warm-up and Johan Djourou took Koscielny's place in the starting line-up.
Wenger explained how the late selection change came about and the Arsenal manager is now waiting for Koscielny's injury to be assessed.
"Koscielny had tendinitis in his knee when he woke up this morning," said Wenger. "I don't know what position he slept in but he could not walk properly.
"He tried in the warm-up but could not play.
"We decided in the morning when he woke up. He came to see me and said he was not sure that he could play with that pain.
"So we called somebody up and pushed him in the warm-up. Straight away after the first run he said he could not even move. How bad it is we have to assess."