Manchester United defender Harry Maguire is set for an extended period out after suffering a hip injury.
The number of matches Maguire will miss is unknown.
But the concern for United is that his absence proves far longer than suggested on Tuesday by manager Ole Gunnar Solskjaer, who said the injury was "not a long, long-term one".
Maguire suffered the injury during last Saturday's goalless FA Cup third-round tie against Wolves.
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The England international completed the full 90 minutes at Molineux, having told his manager he was happy to continue, although he was not walking freely as he left the stadium.
He missed Tuesday's Carabao Cup semi-final first-leg defeat by Manchester City at Old Trafford, after which United face a home FA Cup replay against Wolves, two Premier League matches - at Liverpool and at home to Burnley - and the second leg of their tie against Pep Guardiola's side.
United are already facing defensive injury issues, as both Axel Tuanzebe and Eric Bailly are out, while Chris Smalling is on loan at Roma.
Victor Lindelof and Phil Jones played in Tuesday's defeat by City, with the latter man suffering cramp near the end of the 3-1 defeat.
At the start of the season, defence was the one area United felt confident about in terms of squad strength; their transfer plans for January remain focused on trying to bolster their midfield, where they are considering a move for Ajax's Dutch international Donny van de Beek.
Although Old Trafford sources have consistently stressed the difficulty of signing players during January, there is a feeling Ajax's exit from the Champions League at the group stage gives them some chance of success with Van de Beek.
There is also an acknowledgement that without reinforcements, Solskjaer will struggle to qualify United for next season's Champions League.