World No. 1 Rory McIlroy has confirmed that his ankle injury will prevent him from defending the WGC-Bridgestone Invitational next week.
McIlroy won at Firestone Country Club 12 months ago as part of a superb 2014 run that also saw him win two majors: the British Open and PGA Championship.
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However, McIlroy was unable to play at The Open Championship in St. Andrews earlier this month after rupturing ankle ligaments playing soccer with friends.
And he has now said that he will be unable to compete at the Bridgestone Invitational, which starts on Aug. 5.
"Unfortunately, I will not be defending my World Golf Championships-Bridgestone Invitational title," McIlroy said in a statement on the PGA Tour's website.
"Best of luck to all the competitors, and I look forward to returning to Firestone in 2016."
McIlroy, who has four top-10 finishes at the tournament, remains a significant doubt to defend his PGA Championship title next month at Whistling Straits in Kohler, Wis.
His absence also opens the door for Jordan Spieth to take over as No. 1 in world golf rankings.
Spieth has had a superb 2015, winning the the Masters and U.S. Open before missing out on a playoff at St. Andrews by a single stroke.
McIlroy, from Northern Ireland, took over No. 1 with the victory at Firestone last season, and Spieth can now do likewise if he finishes on top.
American Chris Kirk will also sit out next week's tournament. He has yet to recover from breaking a hand before the British Open.