Marcus Rashford will undergo a scan on his knee before Manchester United can determine the extent of any injury.
The striker was taken off in the latter stages of his side’s FA Cup winner over Liverpool.
He proceeded straight down the tunnel at Old Trafford after being replaced by Anthony Martial.
Ole Gunnar Solskjaer was hopeful that his forward had not sustained a serious injury but admitted he wouldn’t be any the wiser until tomorrow.
“Let’s hope so,” he said when asked if Rashford was okay.
“His knee was bothering him. So a scan tomorrow and we’ll see where we are.”
Rashford scored one and assisted one of United’s three as they saw off the Reds in a classic cup tie.
The 23-year-old was a constant menace from the left and his incredible ball set up Mason Greenwood to level proceedings.
He then put United ahead in the second-half when he was put through.
Solskjaer revealed that he asked Rashford to play in a way that would cause Liverpool’s makeshift defence problems and that turned out to be the case.
He added: “Marcus has played a little bit up front, down the right and down the left.
“We felt if we could switch the ball early today to either side, we could attack them, because Liverpool defend on the front foot and you’ve got to be quick on the ball. I thought we did that well.”
Bruno Fernandes eventually got United’s winner after Mohamed Salah twice scored for Liverpoool.
It sets up a fifth round home tie against West Ham, who are led by former manager David Moyes.
United continue to go from strength to strength and Solskjaer is pleased that his side have settled into a rhythm of playing.
“For us it’s a good feeling, to play on our terms,” he said.
“We’ve found a way of playing that we believe in, that the players believe in. We are getting stronger and stronger.”