Hugo Lloris sustained a dislocated elbow in Tottenham's 3-0 defeat at Brighton, the club have confirmed.
The Spurs captain spilled a Pascal Gross cross at the feet of Neal Maupay, who tapped in to give Brighton a third-minute lead at the Amex Stadium.
Lloris landed awkwardly on his left arm, stayed down for around five minutes and was given oxygen as he was stretchered off.
The France goalkeeper went to hospital, and early on Saturday evening Tottenham released a statement confirming the extent of Lloris' injury.
"We can confirm that Hugo Lloris sustained a dislocated elbow during today's match against Brighton," the statement read.
"Our club captain was stretchered off as a result of the injury and will now return to London this evening after being assessed at a local hospital.
"Assessment will continue this coming week to ascertain the full extent of the injury and the length of time he will require to undergo rehabilitation."
Speaking after the game, Tottenham boss Mauricio Pochettino indicated Lloris' injury was a severe one.
"The news is not good from the hospital, but we need to wait," he said. "Through the website, they are going to explain the situation properly.
"But of course everyone saw on the pitch when he landed, it was not a good situation and the news is not so good."
The incident preceded a poor performance from Spurs, who put in one of their worst displays under Pochettino and a double from Aaron Connolly made it an afternoon to forget on the south coast.
Pochettino felt Lloris' injury happening so early in the game affected his side.
"Of course, we cannot lie," he added. "To concede after three minutes in the way we did and what happened to our captain, it is normal that the impact was massive for the team.
"It is an emotional game and the team was very affected, we never can be in the game.
"We did not show our real performance, I am never going to take the credit away from Brighton, we need to give them the credit too, the team suffered a massive impact after three minutes.
"In the second half we tried to find a different way to play to find a solution, we started the second half well, but we didn't score.
"You need to be lucky to score and be in the game. At 3-0 everyone saw the game was over and there is nothing to do after.
"I feel sorry for our fans, I want to say thank you for the massive effort coming here, we know how they feel, very disappointed, everybody feels really bad, the players and staff are the same.
"We need to find a way to stay together and be all together again and find a good dynamic."