Victor Lindelof handed Ole Gunnar Solskjaer a pre-season scare by hobbling off injured.
The Manchester United defender limped out of the clash with Inter Milan before the hour mark and was replaced by Phil Jones.
Lindelof was seen clutching his thigh as he was accompanied by a physio down the tunnel, where he was going to be checked for further treatment.
The Swede is expected to play a key part in Solskjaer's team this season - and could now miss the start of the season if the problem is deemed anything serious.
Following the game, Solskjaer said of the injuries to both Lindelof and youngster Tahith Chong: "We don’t know yet... I think they should be OK.
"We’ll have to assess it (Lindelof) tomorrow. I don’t blame the defenders for trying to stop him (Chong).”
Lindelof has been linked with a move away from Old Trafford this summer, with Barcelona said to be interested.
But he moved to reaffirm his commitment to United earlier this week after receiving reassurances about his position from Solskjaer.
"I'm very, very happy to be a Manchester United player," Lindelof said, before the team travelled to Singapore for the Inter Milan friendly.
"I'm really looking forward to this season. I'm very excited for a new season to start.
"That's my answer, I'm very happy here.
“I always felt like a Manchester United player but last season was a better season for me, I performed better than I did in my first.
“I'm happy that people think that [I'm the best central defender at the club].
“I'm just trying to do my best every day and that's what I work hard for every day to help the team and the club.”
