Ole Gunnar Solskjaer insisted Paul Pogba was doing everything possible to get fit for Manchester United amid ongoing speculation over his future.
Pogba has not played since September and appears likely to remain on the sidelines when United faces Watford at Vicarage Road on Sunday.
The midfielder battled an ankle injury before a poorly timed illness, diagnosed upon his return from brother Florentin's wedding in France, further delayed his comeback.
Solskjaer recently said the rumoured Real Madrid target would not be sold in January and remains confident about his commitment to the club.
"All I can say is that Paul is working as hard as he can to get back and you will see him smile again as soon as he's back on the pitch," Solskjaer told reporters.
"He is a Manchester United player, someone we are really happy to have in the squad and one of the best players in the world, but he needs to be fit.
"Everyone is allowed to be injured from time to time. I was out for 18 months once and of course I attended weddings and did all sorts of different things during that period, but it was still a bad time for me because I wasn't playing football.
"Being out for a long time like Paul is the worst thing that can happen to a player because everyone wants to play.
"It's a proper mental test for a footballer because there's nothing more disheartening."
United and Solskjaer hope to have World Cup winner Pogba back in a matchday squad before the end of 2019.
That leaves the Premier League games against Newcastle United and Burnley as potential targets if he fails to feature at Watford.
"He's back in training, that's a step forward for us. I'm not going to push him. It depends how he feels," Solskjaer said.
"When he's fit, he's fit. Obviously it's frustrating to be without a player of his quality for so long, but it's part of football. You always want to play your strongest team but you have to plan for different scenarios.
"The rest of the team have stepped up and done well while Paul has been out."
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