Paul Pogba faces "a few weeks" on the sidelines after suffering a thigh injury in Manchester United's 3-3 draw against Everton on Saturday.
The midfielder was forced off in the first half at Old Trafford and a scan has now confirmed the extent of the issue.
Pogba is now set to miss Tuesday's FA Cup tie with West Ham, Premier League fixtures against West Brom and Newcastle and the Europa League double header against Real Sociedad.
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Ole Gunnar Solskjaer told MUTV: "It's an injury that will take a few weeks to heal.
"He's just started his recovery, working with the medical staff and we'll get him back as soon and as safely as we can.
"Of course, Paul has been very important for us and we're not going to take any risks. [So it is] a few weeks definitely.
"You never want to be injured and especially now Paul was really finding his form and enjoying his football. For us, we just have to take as many points and wins as possible when you lose players.
"We've been very healthy and strong for a long period so we can't moan too much."
Pogba has established himself as a key player for United since returning from a previous injury in December, despite his agent Mino Raiola saying in the same month that his client needed to "change teams".
The 27-year-old - whose contract expires at the end of next season - has started 11 of United's last 14 Premier League games and scored decisive goals in wins over Burnley and Fulham.
Speaking last week, Solskjaer said United are keeping an "open dialogue" with Pogba about his future.
The France international has been the subject of regular speculation ever since returning to Old Trafford from Juventus in 2016 for a then world-record fee, thanks in no small part to comments by his outspoken agent.
United triggered the one-year extension clause in Pogba's deal earlier this season, and he said last week said he would "speak with the club and see what's going on".
"Speculation about Paul is always going to be there," Solskjaer said. "We've got a good, open dialogue with Paul. What we talk about and how we see that situation remains between us of course.
"I'm just happy he iss focused, he's playing really well and he's happy in himself and that's important. You can see Paul now enjoying playing football with a red shirt on."