"He's been working really hard to get fit from his injury that he sustained against Liverpool," the Red Devils boss said.

"Then he came back, and he got a different one here in training because he's been really putting a lot of work in.

"And, unfortunately, that's come at a time where, as you say, there are contract talks but that's ongoing, so I can't really comment too much on how far they have come down the line and what he's deciding.

"Well, you have to ask him (if there is any chance of him staying). I don't know how they've been, the last few talks, but we've let him focus on his fitness as well.

"He loves to play and he's not very happy when he can't help his team-mates and he's always giving his all – it doesn't matter if he's got five years left of his contract or five weeks."

Herrera is ruled out of Saturday's Premier League clash against West Ham with a muscle complaint sustained shortly after recovering from a hamstring injury.

Solskjaer, rather surprisingly, suggested that those injury issues could have been contributed to by the uncertainly over his future.

"Maybe the future might have been worrying him and maybe that's part of the reason that he's injured," the United boss said. "Who knows?

"He doesn't know because he got a different injury in training. Hopefully he can be available for around about Chelsea (April 28), City (April 24) but I'm not sure because he got another muscle injury."

Herrera is one of a number of absentees for this weekend's match against the Hammers, with Nemanja Matic likely to be laid low again by illness.

Luke Shaw and Ashley Young are suspended but Matteo Darmian is available and Marcos Rojo could well come in at left-back for his first start under Solskjaer.

Eric Bailly and Antonio Valencia also look set to miss out once again, so too forward Alexis Sanchez as he returns from an ankle injury.

"He is training with us," Solskjaer said of the Chile forward. "He's trained twice. He'll train today.

"I'm not sure if he's going to be available. He's injury free but I am not sure if he's 100 per cent for tomorrow, maybe more likely for the Barcelona game (next Tuesday), so let's see."

Solskjaer will have half an eye on Tuesday's trip to the Nou Camp when selecting his side on Saturday, although he is well aware of the need to win.

Already three points off the top four heading into the weekend, United have lost four of their last five matches in all competitions.

"You're never happy when you don't win games, but it's been a period now where we've played some good teams," Solskjaer said.

"We had some good performances, but we haven't had the quality in front of goal and belief maybe in front of goal that we should have because against Wolverhampton and Arsenal, the two league games, two of the last three, we should have won with the amount of chances.

"So, we've been practising. As a striker I know how important that little belief is and trust in yourself, so we've been putting balls in goals."

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