Phil Mickelson might not get the chance to defend his title at the Waste Management Phoenix Open this weekend.
Mickelson withdrew from the associated Pro-Am event, which is set for Wednesday. The Phoenix Open is scheduled to begin a day later.
Mickelson withdrew from last weekend's Farmers Insurance Open at Torrey Pines with back pain and sought the help of a specialist.
The Associated Press reported that Mickelson will test out his back on Wednesday with a light practice session before making a final decision on the weekend.
"If it was any other tournament, I'd skip it," Mickelson said, "but I'm defending, (Phoenix is) my second hometown and I love the event. I'll have a light practice session and if it goes well I may try to play."