Eric Bailly was forced to leave Wembley in an oxygen mask after suffering a serious head injury.
Centre back Bailly clashed heads with defensive partner Harry Maguire late in the first half of Manchester United's FA Cup semi-final with Chelsea.
It was the second time Bailly had clashed heads during the opening 45 minutes.
The Ivorian initially got straight up after the contact with Maguire, but stumbled and was given treatment on the field of play.
After a period of treatment he he eventually moved off the field on his feet, aided by two members of United's medical staff.
However, as he received more medical care on the touchline, Bailly stumbled and was immediately laid on his back by medics.
Lying on his back he was given oxygen before a neck brace was put on him and he was placed on a trolley.
He was promptly taken down the tunnel and straight to a local hospital, Man Utd confirmed.
Play was halted for nine and a half minutes and both sets of players applauded the 26-year-old when he was wheeled off on a stretcher.
Post-match, Ole Gunnar Solskjaer confirmed: “Yeah, he’s in hospital going through all the routine checks and protocols, he got a cut in the back of his head as well, I haven’t heard, not spoken to the doctor about it yet.
“It had a big impact on the game, Eric played well and we conceded just after the restart and that was very disappointing.
"Eric was a big part of us not having any chances against us, really.
“Obviously the long lay-off was a big test and we didn’t pass it, because we lost our concentration and conceded a goal before half-time, which is disappointing.”
Bailly's injury forced Solskjaer into a formation change as he ditched an ineffective five-man back line to introduce Anthony Martial as an extra attacker.
But in the additional time to the first half, Olivier Giroud opened the scoring to give Chelsea the lead.
Mason Mount doubled Chelsea's lead early in the second half before a Harry Maguire own goal made it 3-0.
Bruno Fernandes scored a late penalty consolation, but it is the Blues who will face Arsenal in the FA Cup final at Wembley on August 1.
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