San Antonio - With the Masters looming in less than two weeks, Phil Mickelson pulled out of the third round of the US PGA Tour's Texas Open on Saturday with a pulled muscle.
Mickelson was one-over for the day after three bogeys and two birdies when he withdrew on the par-five second hole, his 11th of the round.
His caddie, Jim Mackay, told a television interviewer that when the player teed off at the first hole, his 10th of the day, he "just felt a little pain in his side".
After continuing for a few minutes, Mickelson opted to play it safe with the first major tournament of the year starting at Augusta National on April 10.
Mickelson "just decided he didn't want to take anything to chance relative to what's going on the next couple of weeks," Mackay said.
Mickelson, whose five major titles include three Masters green jackets, has had a slow start this season.
A back problem forced him out of Torrey Pines in February, and he hasn't had a top-10 finish in eight starts including this week.
He entered the Texas Open for the first time since 1992 in a bid to play more competitive rounds before the Masters.
He birdied his last hole on Friday to make the halfway cut on the number and said he was pleased with how he was hitting the ball.
"I'm hitting the ball hard, I'm hitting it high, my speed is back, my back feels great, my body feels great, and I'm able to hit the ball hard again," Mickelson said Friday.
It wasn't immediately clear whether Mickelson would go ahead with plans to play in next week's Houston Open, which he won in 2011.
Mickelson isn't the only marquee player fighting to get fit for Augusta.
World number one Tiger Woods is receiving treatment for back spasms and said on Monday he wasn't sure if he'd be ready to play at Augusta.
Woods, a 14-time major champion chasing the all-time record 18 majors won by Jack Nicklaus, withdrew from this month's Arnold Palmer Invitational at Bay Hill, where he had won eight times including last year, due to nagging back pain.
Woods won the last of his four Masters title in 2005.
He has not won any major title since the 2008 US Open at Torrey Pines, when he limped through an 18-hole playoff to defeat Rocco Mediate.