AP

CHERRY HILLS VILLAGE, Colo. (AP) — Keegan Bradley made a decision that could cost him a chance at $10 million by withdrawing from the BMW Championship on Saturday, more than 24 hours after taking a drop he wasn't sure was legal.

Bradley's approach to the 18th green in the first round on Thursday embedded in a pitch mark and he took a free drop. Players get the free drop if the ball comes to rest in its own pitch mark, but Bradley spoke with a fan near the green who told him the ball bounced and came to rest in a different pitch mark.

Bradley had doubts about the ruling heading into Friday. He discussed the drop with a U.S. PGA Tour rules official, who absolved him of any wrongdoing, but even after that, Bradley said it didn't feel like the right call.

"It's eating me alive," Bradley said. "I didn't call my fellow competitors for help in the first place and that bothers me. I know the official approved the drop but I just can't be absolutely sure it was the right spot."

Bradley came into the week ranked 28th in the FedEx Cup. The top 30 after this week's tournament advance to the Tour Championship, where everyone has a mathematical chance at the $10 million first prize that goes to the FedEx champ. With the third round underway, Bradley's projected standing had fallen to 35th. Those numbers will change through the weekend.

Regardless, the 2011 U.S. PGA champion, who will play the Ryder Cup as one of Tom Watson's captain's picks, felt he did the right thing.

"I just feel withdrawing is the right thing to do to protect the field in the BMW Championship and the Tour Championship next week," Bradley said.

Earlier, Phil Mickelson also withdrew from the BMW. He said he wanted to rest to prepare for the Ryder Cup. He was 14 shots out of the lead and needed to finish at least fourth to have a chance to advance to the Tour Championship.