Rory McIlroy missed the chance to become the new world number one as he lost 2&1 to Hunter Mahan in the Accenture Match Play final in Arizona.
Knowing victory would see him knock Luke Donald off top spot, McIlroy never hit the heights in his 18-hole final with American Mahan until it was too late.
The US Open champion had already halved two holes in bogeys when Mahan broke the deadlock with a tee shot to two feet on the sixth.
McIlroy then double-bogeyed the 486-yard next, seeing a chip come back to him after both men had rolled down the slope in front of the green with their approaches, and then had another six on the long eighth after driving into a bunker and going long with his third.
Mahan went three up there despite three-putting for par and when both parred the next he had turned in a level-par 36 to McIlroy's 39.
The gap became four when McIlroy missed from nine feet on the 10th after 29-year-old Mahan had almost holed his approach. Only did then the player from Holywood spark into life.
He chipped in for eagle at the 11th and had a hat-trick of birdies from the 13th. That was the good news for his fans, but the bad was that Mahan matched two of the birdies and after lipping out for victory from 15 feet on the short 16th, another par on the next settled it.
Mahan made 35 birdies during his six games this week and said: "I felt great with my game coming in. I made a putter switch to the PING Nome putter and felt great on the greens immediately. I got hot there in the middle of the week and was able to run it out."
"We didn't have our best stuff early, we didn't play great and I was able to capitalise on a couple of miscues but Rory's a great player. He's the best player in the world right now for sure and I knew he was going to make a charge and he did and felt pretty proud to hold on like I did."
Mahan said improvements in his short game were the key to victory. "Ball-striking is a strength of mine but I have to chip and putt if I want to win and I felt like that was a strength this week and that was definitely a huge key."
McIlroy reflected: "I played a great back nine which was nice but I just left myself too much work to do from the front nine.
"From the first hole I had a chance from about four feet to go one up and I missed that. There was a little stretch around that front nine, sort of five, six, seven, eight where that's probably where I lost the match."
In the third place match, Mark Wilson defeated Lee Westwood 1up.
Westwood could also have gone to number one this week but lost his semi-final to McIlroy 3&1 despite being three up after four holes.
He looked flat in his third place match and the steady Wilson, who lost 2&1 to Mahan in their last-four clash earlier in the day, closed the match out on the final green with a par.