Maguire is set to miss Villarreal's visit to Old Trafford in the Champions League on Wednesday night, having sat out of May’s Europa League final in Gdansk against the same opposition.
United are already without right-back Aaron Wan-Bissaka following his sending off in their opening 2-1 defeat to Young Boys.
“Luke has been in today, I'll give him a chance to be involved. He didn't train with the rest of the team,” Solskjaer said.
“Harry is more or less definitely out, it doesn’t look good. It's his calf. That might take a few weeks. He was of course hoping to play against Villarreal, he missed the last game against them, but that’s football for you.
“It's his calf and that might take a few weeks so let's see how quickly he recovers. He was of course hoping to play against Villarreal, he missed the last game against them, but that's football for you. With Aaron suspended, we'll have to make a few changes.”
Solskjaer is hoping ot arrest a slide that has seen United lose three of their last four games, with last week’s EFL Cup exit to West Ham sandwiched by the Young Boys and Villa setbacks.
“The pressure if a privilege,” Solskjaer said. “To work in this environment, you have to embrace that pressure.
“You're right, it's the group stage and only 6 games, you need 10 points to get through most likely and we lost last time. Atalanta and Villarreal drew, so maybe their point is not good enough for them either.
“If you end up with zero after two games you need to win the last four probably. It's not a must-win game but it is very important.
“After the Young Boys game, if you win one away and your home games you should be through. We'll get a good response from the weekend.”
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