Everton have confirmed that James McCarthy suffered a double leg fracture in his side's 1-1 draw with West Brom on Saturday.
McCarthy was carried off on a stretcher just before the hour mark after he nicked the ball off Salomon Rondon in the act of shooting, and the Venezuelan's follow-through connected with the midfielder's lower right leg.
Rondon and Everton goalkeeper Jordan Pickford both immediately motioned for trainers to come attend to McCarthy, who was in obvious pain.
Medics rushed onto the field to treat McCarthy with Rondon in tears having seen the after-effects close up and Seamus Coleman, only just recovered from a serious double fracture of the leg himself, was seen leaving his seat in the directors' box apparently to be with his Republic of Ireland teammate.
After the incident, Everton said on Twitter that McCarthy had suffered "what looks like a broken leg," and the club confirmed the diagnosis after the game.
"All our thoughts are with James McCarthy this evening after it was confirmed he has suffered a double leg fracture," another tweet said.
Everton boss Sam Allardyce said McCarthy had fractured his tibia and fibula and said he expected McCarthy to be sidelined through the rest of the season and the summer.
"His tibia and fibula have been broken from his really brave efforts to stop West Brom with a possible scoring opportunity. He's paid a heavy price for his commitment there,'' he said.
Asked how soon the player would have his operation he added: "When we do it will depend on the specialist surgeon.
"Obviously it's a big blow for him and us because he's had so many games missed recently with not-so-serious injuries that we thought we had overcome, and certainly had overcome them over the last few weeks.
"Now this is one serious injury which we know will keep him out until next season at some stage, that's a big blow.''
Rondon appeared distraught after the collision and was consoled on the pitch by West Brom manager Alan Pardew.
"Salomon was traumatised," Pardew said. "He heard the break... that affected him because he is that kind of person.
"I wasn't sure he was going to carry on, but he got himself together and fair play to him, he was definitely the best player on the pitch today."