Arsenal manager Mikel Arteta said he is worried about Bukayo Saka's availability for Sunday's league game against Manchester City after the forward went off injured in the first half of their 2-1 Champions League defeat by RC Lens.
Saka was replaced by Fabio Vieira in the 34th minute of Tuesday's game and Arteta said the muscular issue was "big enough not to allow him to continue to play the game and that's obviously a worry for us".
The 22-year-old also limped off the pitch in Arsenal's 4-0 league win at Bournemouth - which was his 87th consecutive Premier League appearance.
Before that, he was rested for a League Cup tie against Brentford last week after picking up a knock in a 2-2 home draw with Tottenham Hotspur.
Asked if he regretted starting Saka amid his injury issues, Arteta said: "No, it was a knock that he picked up the other day, and he was perfectly fine ...
"(Saka's previous injuries) were more knocks than any other thing. The last few that he had, he hasn't really missed games. We gave him a break against Brentford in the League Cup, and that was all."
Arteta has been criticised for not resting Saka often enough but the Spanish manager said all the players had been keen to play against Lens.
"It was a big Champions League night," he added.
"I painted a picture, the scenario, the type of game we are going to have to face today and they all knew about it. But the Champions League is so difficult to win ... and today we take a big lesson as well."