Rory McIlroy slumped out of the WGC-Accenture Match Play Championship after being taken to a 19th hole by American Harris English.
World number seven McIlroy appeared to have victory in his second-round match at Dove Mountain within his grasp as he hit form on the back nine.
The Northern Irishman won four out of five holes to lead by one after 16 but English, impressive winner over Lee Westwood in round one, replied to take the contest to sudden death.
It was at the first extra hole that McIlroy's touch deserted him as he failed to recover from a poor tee shot.
He went wide to the left and could then only pitch into desert rough between a bush and a tree. From there he overshot the green and there was no way back.
It was a disappointing end to a high-quality contest in which few other holes had been settled by mistakes.
English twice led on the front nine but his successes on the second and seventh were immediately cancelled out by McIlroy and the match was all square again at the turn.
McIlroy might have rued a missed putt at the ninth that would have put him ahead when English struck out by taking the 10th and 11th.
But McIlroy, whose iron play had been outstanding, found his touch on the greens to win the 12th, 14th, 15th and 16th, all with birdies, and edge ahead for the first time.
But English stemmed that momentum with a birdie of his own at 17 and he held his nerve to prevail on the 19th.
Meanwhile, Graeme McDowell came good when it mattered once more.
The Portrush man beat Hideki Matsuyama on the final hole to progress. He will now play Hunter Mayan, who beat Richard Sterne 2up.
"Why do it the easy way when the hard way will do?" McDowell smiled as he spoke to reporters at Dove Mountain in Marana, Arizona.
"I just got off to a slow start again, probably less so today. Hideki opened up three-three, so I was two down walking off the second green.
"I was quite proud of myself when I got a half on three, so I was only two down after three, as opposed to three down. But I made a bad swing on six, hit it in the right bunker there."
Three down after six holes, McDowell then upped a few gears and recorded five birdies over the closing stretch as he overcame a solid display by the 21-year-old Japanese.
"I played really clean golf," McDowell said of his rallying effort. "I tried to go out there today and execute my game plan and try not to give him any room, try not to make any mistakes.
"And he kind of played the same kind of golf back. He played very, very well. I made big putts on 15 and 16, especially on 16, that was a massive putt to give me the opportunity.
"I feel very fortunate again today. I've certainly expended all my energy and emotions the last couple of days. But thankfully it's early in the season and I've plenty left in the tank."