Marcus Rashford has vowed to return "fitter than ever" after suffering a double stress fracture in his back, ruling him out for at least six weeks.
The 22-year-old suffered the injury coming on as a substitute in the FA Cup replay with Wolves.
"On the pitch or not, Man Utd fans don't get much bigger than me," he said on Twitter.
"You best believe I'll be involved in team meetings, team huddles and team sessions throughout this recovery.
"Blink and I'll be back, fitter than ever. See you soon"
Speaking after Manchester United's 2-0 defeat at Liverpool on Sunday, Manchester United manager Ole Gunnar Solskjaer said: "He has suffered a bad injury. It's a stress fracture, it happened against Wolverhampton.
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"It's unlucky for Marcus, he will be out for a while for us."
Questioned whether Rashford is more likely to be out for months, Solskjaer added: "He won't be back until after the mid-season break. I don't know how long it is, I'm not the doctor.
"Normally a stress fracture is six weeks to heal. Then he needs some recovery and rehab after that probably."
Rashford came on as a substitute in the 64th minute against Wolves but was forced off just over 15 minutes later after a collision with Matt Doherty.
Solskjaer added that Rashford's injury could force United into the transfer market and that loan deals were an option.
"It's an unfortunate situation we are in," Solskjaer told Sky Sports.
"We might look at some short-term deals as well.
"If there are the right players there and they fit, we can buy. If there are loans available, that might be possible."
Analysis: Manchester United have to buy a new striker
Sky Sports' Gary Neville...
"United have to go into the market. They need someone up there with a physical presence and a bit more maturity - and they need another body.
"They have struggled to get into the market for a centre-forward. They desperately needed a striker to replace Lukaku and they haven't been able to get one."