San Francisco - Phil Mickelson withdrew from the upcoming World Golf Championships Match Play Championship on Sunday for personal reasons.
The five-time major champion said he was sorry to miss the elite event, which is moving this year to Harding Park in San Francisco.
"TPC Harding Park is a terrific setting for match play, so it's unfortunate that I won't be able to play this year," he said.
The 44-year-old American left-hander is the third player from the top 64 in the world to pull out of the event.
England's Luke Donald and South African Tim Clark are the other two.
Mickelson's withdrawal opened a place for Finland's Mikko Ilonen in the field.
Mickelson has played the WGC Match Play 11 times since 1999.
He lost in the first or second round five times, and his best finish was a quarter-final loss to fellow American Davis Love in 2004.
The 44-year-old is coming off a runner-up finish at the Masters.
That was his first top-10 finish of the season, and first since his runner-up finish at last year's the PGA Championship.
This year the tournament has a new format featuring round-robin play in 16 four-player groups, so that an early match defeat doesn't mean an automatic exit.
The player with the best record in each group advances to the knock-out round of 16.