Paul Pogba will miss "a few weeks" for Manchester United, Ole Gunnar Solskjaer has confirmed in concerning news ahead of a key month.
World Cup-winning midfielder Pogba returned to United's starting line-up to face Everton at the weekend but lasted just 39 minutes of the 3-3 draw.
The 27-year-old appeared to suffer a thigh injury and was quickly deemed a doubt for Tuesday's FA Cup fifth-round clash with West Ham on Tuesday.
Solskjaer has since revealed the extent of the issue, which could keen Pogba out of a series of big matches.
United play Real Sociedad home and away in the Europa League in February, before visiting Chelsea in the Premier League at the end of the month and Manchester City on March 6.
"It's an injury that will take a few weeks to heal," Solskjaer told MUTV. "He's just started his recovery, working with the medical staff and we'll get him back as soon and safely as we can.
"Of course, Paul has been very important for us and we're not going to take any risks. [It will be] 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 scored winning goals at Burnley and Fulham in January, although United's form has since suffered a little, allowing City to build a five-point gap at the summit with a game in hand.
Meanwhile, Solskjaer suggested that captain Harry Maguire could be given a rest against West Ham, having sat out just two games since the campaign started.
"Of course I think about if he needs a rest, if he physically can keep going and going," said the United boss.
"The nature of a centre-back position is a different position compared to full-backs and wide men or even central midfielders, or any other position on the pitch. The centre-backs are the ones who are protected mostly from the real fatigue because you're working less.
"Then again, he's never injured, Harry. He's never been really badly hurt, touch wood, and hopefully he'll be able to carry on. But I'm not sure if he'll play on Tuesday or not. I've not decided yet."
United have scored 12 goals across their past two games and although Mason Greenwood did not find the net in the 9-0 win over Southampton or the draw with Everton, Solskjaer has been impressed by his recent displays.
Greenwood created two chances – one of which ended in an assist – and had two efforts on target against Southampton, while he also completed three dribbles. Versus Everton he failed to hit the target or supply a key pass, but was again successful with three of his five attempted dribbles.
"Mason was different class [against Everton]. I thought he was the standout performer on the pitch - he just didn't get the goal that his performance deserved," said Solskjaer.
"I think the last few games, if you look at him closely - yeah, I know we scored nine against Southampton - but if you look at his performance, I thought his performance was top.
"He's improved and matured immensely, and he's working with some of the top forwards in the country, of course. He's learning off them, and it's exciting to see that he's come over his blip and is playing really well."