Alex Lacazette was forced off during the second half of Sunday's 1-1 draw against Fulham.
The French striker, in fine form of late with two goals in each of his previous two appearances, pulled up off the ball after sprinting towards the box during an attack.
Lacazette was replaced by Eddie Nketiah shortly afterwards, and Mikel Arteta gave an update on his condition after the game.
"Lacazette has done his hamstring, it's not good news," he told Arsenal Media.
"That's why we rotated some players, because some players weren't recovered yet. But we cannot change all the players, so it's tough to see."
Shortly after that interview, Arteta sat down for his post-match press conference and was asked again about Lacazette.
"We'll have to see [how long he will be out for]," he said. "We'll have the scan, probably on Tuesday, to see the extent of the injury and the timeline for it. But I don't know.
"I cannot tell if it's going to be a week, two weeks, five weeks or six weeks. He felt something in his hamstring and we don't know the extent of it. We are all disappointed because we all know the moment that Laca was on."
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