Michael Carrick has said Luke Shaw will be assessed before deciding whether the defender is fit to face Manchester City.
Shaw was left out of the 4-0 win over Sabah FK on Thursday after being forced off in the 2-2 draw with Everton.
The 31-year-old started every Premier League game last season, but he's in danger of missing Sunday's Manchester derby if he cannot prove his fitness.
"We'll have to see," Carrick said.
"We just kind of looked after him a little bit. He wasn't quite ready for [Sabah] 100%, so we didn't risk it. We'll see how he is over the next couple of days or so."
City's visit to Old Trafford is a repeat of Carrick's first game in charge after taking over from Ruben Amorim on an interim basis in January.
United had gone four games without a win before the derby, but produced a stunning performance to beat City thanks to goals from Bryan Mbeumo and Patrick Dorgu.
"It'll definitely be different, just because no games are ever the same," Carrick said.
"I think there's no way we're assuming we won last year, we'll do the same things and everything will be the same.
"I think the confidence that we've built over a period of time and feel like we're getting better all the time, I think that helps us.
"We know it's a big game, we know it's an important game. There's a lot riding on it, it's pretty obvious to say, but we're looking forward to it. We've got a short space of time to recover and prepare for it, but we'll make the most of it."
Carrick was given a contract until the end of the season when he was appointed in January. Victory over City contributed to a run of 12 wins from 17 games to win the job permanently.
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There was an initial expectation that United would appoint an outside candidate in the summer, but Carrick insists he was always thinking long-term.
"I think I said it pretty early on, I was always planning to be [manager beyond the summer]," he said.
"All the decisions we were making were if we were going to be here for a period of time. I never knew how long that was going to be, I still don't!
"But you're always planning for the future, what we want it to look like and the direction we want to go, and that was from day one.
"The performance the lads gave was incredible with all that, but there was definitely always -- has been, always will be for me -- from the start was planning to try and get this club to where we want to get it in the long term."
