Dani Carvajal has confirmed he will need surgery after suffering a "serious" cruciate ligament injury in Real Madrid's 2-0 win over Villarreal at Estadio Santiago Bernabeu.
The Spain right-back was left screaming in agony after seemingly over-extending his knee in a collision with Yeremy Pino in added time, and was carried off the pitch on a stretcher in tears.
"Serious cruciate ligament injury confirmed, I'm going to have to go through surgery and be off the field for a few months," Carvajal, 32, later wrote on Instagram.
"Already looking forward to starting recovery and coming back like a beast."
Speaking immediately after the win which continued Real's unbeaten start to the La Liga season, manager Carlo Ancelotti said his players were "sad" and "worried" for Carvajal.
He added: "Something happened that happens a lot, because of the calendar, and it happened to a very, very important player for us."
A Real Madrid statement, external on Sunday said that Carvajal had "a ruptured anterior cruciate ligament, a ruptured external collateral ligament and a ruptured popliteus tendon in his right leg" and would have an operation in "the coming days".
The Spanish club later announced that Carvajal, who has won the Champions League six times and La Liga four times with the club, has extended his contract with them until 30 June, 2026.
"Real Madrid would like to show him all its support and affection and wishes him a speedy recovery so that we can enjoy his football on the pitch again as soon as possible," said the Bernabeu outfit.
Meanwhile, the La Liga side said that Brazil forward Vinicius Junior had suffered a neck injury and his "progress will be monitored".
Real's victory came after a shock defeat by Lille in the Champions League on Wednesday.
Federico Valverde gave Real the lead in the 14th minute on Saturday when his shot from the edge of the box found the bottom left corner after deflecting off the unfortunate Alex Baena.
Moments later, Villarreal almost equalised when Nicolas Pepe's header clipped the crossbar from Baena's cross, before Thierno Barry headed over the bar.
Vinicius Junior made sure of the victory with 17 minutes left to play, launching a fierce effort from long range into the top corner.
Real had further chances to increase their lead but Antonio Rudiger sent a header over the bar and England international Jude Bellingham's long-range effort sailed wide of the post.
Villarreal thought they had a penalty five minutes after the break when Aurelien Tchouameni fouled Barry, but the French forward was adjudged to be offside.
Baena's 25-yard free-kick grazed the side-netting as the away side continued to probe but ultimately failed to find a way back into the game.
Ancelotti's side are now undefeated in 41 La Liga matches (W30 D11), the second best unbeaten streak by a team in the entire history of the competition.
Rivals Barcelona are the only side to better that, with a 43-game unbeaten league run (W34 D9) in 2018.