Cape Town - James McCarthy's season ended on Saturday with a double leg fracture during the 1-1 draw with West Brom.
The Everton midfielder was stretchered off after a tackle on Salomon Rondon with an hour played. He was replaced by Wayne Rooney.
Speaking after the game, Toffees boss Sam Allardyce confirmed fears of a break.
He said: "It's a tibia and fibula fracture compounded. A very nasty injury."
The Republic of Ireland international had only returned from an injury in December and was playing just his third game of the season.
Allardyce added: "We had just worked hard to get him back to fitness. It's a loss to us until the end of the season - it happens in the game of football but not often that severe."
West Brom boss Alan Pardew, meanwhile, said that Rondon was distraught following the incident.
He said: "I saw his reaction straight away, he must've heard something, sometimes it does really affect you and it did it take us a while to get him round and focused again.
"Our thoughts go with James and we wish a speedy recovery to him."
Rondon immediately after the game posted a heartfelt message to McCarthy on Twitter saying he was devastated by what happened and wished him a speedy recovery.
Absolutely devastated. Rivalries are forgotten about when a colleague suffers such an unlucky injury. Really hope to see you back playing again soon, @JMcCarthy_16.#GetWellSoonJames pic.twitter.com/pamazH8fCO— Salomón Rondón (@salorondon23) January 20, 2018