Rory McIlroy has ruptured a ligament in his ankle while playing football with friends at the weekend.
The World Number One golfer from Holywood took to social media to share a picture of himself in crutches with his foot in a cast boot.
He said:" Total rupture of left ATFL (ankle ligament) and associated joint capsule damage in a soccer kickabout with friends on Saturday. Continuing to asses extent of injury and treatment plan day by day. Rehab already started.
"Working hard to get back as soon as I can."
McIlroy has not ruled himself out of next week's Open Championship at St Andrews, a spokesman for the golfer said.
The Northern Ireland golfer is due to take part next week in the the 144th Open where he is set to defend his title.
Rory McIlroy was at his brilliant best when The Open returned to Royal Liverpool in 2014.
The Co Down man led from start to finish, becoming only the third player in the history of the sport to win three Major Championships by the age of 25 after Jack Nicklaus and Tiger Woods.
Former Ryder Cup captain Sam Torrance was taken by surprise by the news as he arrived at Wimbledon to watch the day's action there.
"That's the first I've heard of it but I'm in complete shock: that's a big blow to (the Open) if he misses it," Torrance told Press Association Sport.
"That's obviously bad news and I'd just wish him all the best and hope he can make a quick recovery."
Paul McGinley, McIlroy's captain at last year's Ryder Cup, heard the news as he visited Wimbledon on Monday and expressed his disappointment at the prospect of McIlroy not featuring at the 'home of golf'.
McGinley said: "I'm sure he'll be very disappointed. I'd like to find out a little bit more because sometimes these injuries can settle down very quickly. But it'll be a blow not just for Rory but a blow for the game as a whole.
"He's performed very well in the two majors so far this year. I know Jordan has taken all the plaudits in terms of winning but two top-10 finishes for Rory in the majors is a pretty good effort.
"I know St Andrews is a golf course he really loves and a golf course that really suits his game. It's a shame, a shame for the tournament and a shame for Rory if that's the case."
Recovery from injuries such as the one reported by McIlroy can take weeks or, in the worst cases, months and even require surgery. McIlroy has as yet given no details on the anticipated timescale for his recovery.
Should he be sidelined and be out of action for more than a month, he could be unable to defend his title at the US PGA Championship at Whistling Straits, which begins on August 13.
McIlroy has been only on the fringes of challenging at this year's majors, both won by Jordan Spieth. At the Masters in April he finished four strokes back while he finished tied ninth, five shots off the pace, at last month's US Open at Chambers Bay despite a final-round 66.
Much has been made of a potential rivalry with 21-year-old Spieth, who has risen to number two in the rankings, but the injury could prevent any head-to-head meetings in the remaining two majors of the summer.
