Manchester United lost Marcus Rashford to injury as it beat Wolverhampton Wanderers 1-0 in an FA Cup third-round replay at Old Trafford.
Star striker Rashford started from the bench just four days before a crunch Premier League clash with leader Liverpool, but he was introduced as a substitute three minutes before Juan Mata scored the only goal on Wednesday.
The England international appeared to be nursing his back and, after initially attempting to play on, had to be replaced with 10 minutes remaining.
The issue provided a disappointing end for Ole Gunnar Solskjaer, whose side came through a replay after drawing the first clash 0-0 earlier this month against the opponent that knocked it out of the cup last year.
A lively opening saw John Ruddy crucially bat the ball to safety as Daniel James bore down on goal following Mata's gorgeous lofted pass, before Raul Jimenez twisted into space in the United area but shot straight at Sergio Romero.
United was fortunate to see a Wolves goal ruled out in the 10th minute, as Fred hopelessly hacked a clearance into the legs of Nemanja Matic, allowing Jimenez to challenge Harry Maguire and inadvertently control with his arm before Pedro Neto slid the ball into the net.
Ruddy saved low from Mata and blocked bravely from James either side of Matt Doherty heading against the base of the left-hand post after a short Wolves corner in an even first half.
James drilled across the face of goal early following the restart, but second-half chances were sporadic until the decisive goal.
United responded to its counter-attacking opponent with a break of its own, Anthony Martial timing his pass well to keep Mata onside and he produced a delicate dink over Ruddy.
However, then came the Rashford blow, the forward going down following a challenge with Doherty and never regaining full fitness, hobbling off for Jesse Lingard to provide Solskjaer with concern before the Liverpool clash.
What does it mean? Big concerns for either side
Rashford has 14 Premier League goals this season and will be a big miss if he cannot make the Liverpool game or any subsequent key matches, including an EFL Cup semifinal second leg against Manchester City.
But Wolves were also left with a major concern late on as Adama Traore, their own talisman, pulled up before a swift substitution. Two teams engaged in Europa League campaigns look to be feeling the workload.
Mata makes mark
Although chances came thick and fast for much of the first half, this contest looked destined to end goalless - as in their previous meeting - until Mata intervened.
He created the game's first big chance and finished its last, coolly sitting Ruddy down and finding the net.
Neto not on it
Teenager Neto thought he had a goal to remember in the early stages, but this was not his night.
The winger struggled up against Brandon Williams, the two tussling off the ball at one stage, and wasted a great opportunity to feed Traore on the counter seconds before he was substituted.
While United is through to face Watford or Tranmere Rovers in the fourth round, both sides are first back in Premier League action. United faces that daunting trip to Liverpool on Sunday, with Wolves visiting a resurgent Southampton the previous day.