Ole Gunnar Solskjaer admitted it will be weeks rather than months that Paul Pogba will be out injured, but gave the Manchester United midfielder a target return date of just after Christmas.
Pogba suffered the injury in training while on international duty with France last week ahead of their World Cup qualifiers against Kazakhstan and Finland.
The midfielder is already unavailable for United's Premier League game at Watford on Saturday as he completes a three-game ban following his red card against Liverpool on October 24, with Solskjaer forced to try to revive the club's fortunes without knowing when Pogba will be able to return to action.
"I would say months rather than weeks," Solskjaer said when asked for Pogba's return date. "It was a disappointing injury for Paul. I'm not a doctor of course and we can't say how quickly it will heal.
- Paul Pogba travels to Dubai to continue recovery
- Jesse Lingard expects to leave Man Utd after talks stall
- Watford vs Man Utd preview: Several concerns for visitors
- Ole Gunnar olskjaer: Added pressure can help Man Utd improve
"Sometimes you hope for six or seven weeks and the worst case scenario is 10, 11, 12 weeks with muscle injuries like this. One thing I'm sure of is that Paul is determined to come back and give his best when he comes back and he's already started that recovery with his own big mentality to come back stronger.
"Hopefully just after Christmas we can see him."
One solution to fill the Pogba-shaped hole at Old Trafford is Donny van de Beek, who has found first-team football hard to come by since arriving in England in the summer of 2020.
Fans were calling for Van de Beek to be summoned from the bench during their side's 2-0 defeat to Manchester City in their United's league match, with Solskjaer admitting the Netherlands midfielder is doing all he can to win his spot back in the first team ahead of Saturday's clash with Watford.
"I think our fans can see a top professional and a very good player and Donny is one that has never ever let himself or his team or his family down by his attitude," Solskjaer added. "His approach to the game and training is spot on and I can't fault him and he knows that.
"I keep in contact and I speak to him and communicate with him because it's not easy when players are not playing as much as they think they should do and Donny thinks he should be playing more and he will be involved.
"I can't say anything other than that he's another example of what to do when you're not in the team and he'll reap his rewards."
Solskjaer also leaped to the defence of Harry Maguire, who has struggled for form this season and drew criticism from former captain Roy Keane for his finger-in-ear celebration when scoring for England against Albania in midweek.
"As a team we've not performed at the standard we know that we can do and at the levels we need to be at," he added. "Harry, as Gareth (Southgate) righty said, he's not one to hide on the treatment table or try to find any excuse to sit out games.
"Harry is a top professional who wants to be there for the manager every single time and he trains really well and I think this week going away and scoring a couple of goals for his country will help his form and confidence.
"For me, no I've not considered taking away any captain's armband away from him. He's been an absolute stalwart for us on and off the pitch since he came in.
"The so-called experts have their opinions and that's their job to put their opinion that's not something we have to worry too much about. As a true example of a Man United player Harry is always there for his team and his country."