Bukayo Saka and Willian both picked up injuries during Sunday's game at Leeds United.
Saka almost snatched victory for us when he raced through in the closing stages, only for Illan Meslier to make a vital save.
But having been such a threat on the counter-attack, Saka was forced off after a challenge in which an opponent's stud appeared to connect with his knee.
Mikel Arteta gave an update on Saka's injury in his post-match press conference.
"He was in pain," said the manager.
"We're going to have to assess with the medical staff how bad it is, but it looked like a pretty bad challenge and he was in pain so we decided to take him out straight away."
Earlier, Willian was replaced by Reiss Nelson at half-time. That was not a tactical decision by Arteta.
"He was feeling something muscular and we had to take him off," he said.
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