Graeme McDowell paid the price for some ragged play as he was knocked out of the Accenture World Match Play in Tucso by Australian Jason Day.
McDowell had earlier come through against the Republic of Ireland's Shane Lowry - the same man who made waves when he dumped McDowell's compatriot and world number one Rory McIlroy in the first round.
But in truth he was some way short of his best throughout the day.
Two birdies in the first three holes against Day briefly gave him hope of winning though but it was not to be.
He looked at sea at times on the back nine - a loose tee shot here, a lack of finesse at the greens there and plenty of apparent frustration.
A player in better touch than Day would have put him away earlier, but as it was he took the lead for the first time at hole 11.
McDowell got back on terms at 14, lost the next hole and then rallied again at 16.
A bogey-five at 17 was the final nail in his coffin, a missed 10-footer from the sleeve of the green representing his last chance.
Day then made a two-putt to go through.
"Every round feels like the Sunday at a tournament" - Jason Day
The 25-year-old spoke of the pressure of the format as he left the course.
"My head is in a well right now," he told Sky Sports 3.
"It's amazing how much pressure there actually is. Every round feels like the Sunday at a tournament when you're in contention and I've played four now.
"Physically and mentally I'm grinding it out there."
Ian Poulter (below) continued his irresistible form as he led the charge into the semi-finals.
Five months on from his superb Ryder Cup showing and three months since he claimed the HSBC Champions competition in China, the 37-year-old Englishman once again proved his match play prowess on a busy two-round day in Arizona.
Having stormed to a 5&3 win over Tim Clark in the last 16, the 2010 winner reached the last four with a 3&2 over Steve Stricker.
He faces reigning champion Hunter Mahan tomorrow in a mouth-watering contest.
Day's semi-final opponent is Matt Kuchar, who was first to book his place with a 3&2 victory over Robert Garrigus.
It was Poulter who caught the eye, though, making five birdies and an eagle at the par-five eighth to leave Stricker little chance on what proved to be a disappointing 46th birthday.
Poulter himself made no secret of his confidence going into championship day.
"There's lots of world ranking points to play for and a nice trophy sitting over there that I'd quite like to take back home," he told Sky Sports 3.
"The short game is on. I feel really confident round this golf course with a lob wedge in my hand.
"I've holed the right putts at the right times. I've made a couple of mistakes only and it's looking good right now."
Kuchar, who ousted Nicolas Colsaerts 4&3 in his first match of the day, ensured he would see action on the deciding day with a 3&2 success over Garrigus.
Kuchar took the lead at the first hole and did not surrender it throughout the match.
He was three up at the turn and four up after birdying the 10th and although Garrigus won back-to-back holes at 12 and 13, Kuchar was in no mood to let the result slip.
Reigning champion Mahan was the last player to confirm his place in the semi-finals.
He edged a low-key encounter with Webb Simpson with a 1-up win.
Birdies were in short supply from both men who each won a hole on the front nine and were all square again after successes after respective successes at 10 and 13.
Mahan made the decisive move with a birdie three on the 16th and sealed victory with a par on the penultimate green.