With a 4-iron in hand, 196 yards from the hole, he went for the green on the par-5. Instead, the ball disappeared in the greenside lake, along with his chance of winning in four different decades on the PGA Tour.
Mike Weir proved the rightful benefactor. He birdied his final three holes to capture the Bob Hope Chrysler Classic.
Weir shot 5-under 67 on a very windy Sunday at PGA West to finish at 30-under-par 330; two shots clear of the 1988 Bob Hope champion, who shot 69.
The victory was Weir's first since the 2001 Tour Championship, and came on the heels of a year when he failed to earn a single top-10 finish.
Along with $810,000, he incidentally became the second consecutive left-handed player (Phil Mickelson) to win the Hope.
Down one, Weir tied Haas for the lead by making a 25-foot birdie at the 17th.
Both men found the fairway at the 543-yard 18th. Hitting first, Weir decided to lay up from 203 yards.
'My only option, really, was to lay up. If I hit 10 balls from there, I might be able to get one on the green,' he said. 'But I felt I could lay it up to 80 or 90 yards, my wedge shot is right into the wind, and I had the bank I could play into.'
The 49-year-old Haas, on the other hand, took the aggressive route, and paid dearly. With the pin tucked on the front left side of the green, guarded by water, Haas approach shot came up short and wet.
'I was between a 4- and 5-iron, and I took the 4. I just mis-hit it a little bit. I was a little surprised it didn't carry,' Haas explained.
It was the second time in as many years that Haas led late in the final round of this event but failed to win.
As for Weir, the native of Sarnia, Ontario, became the sixth straight international player to win a PGA Tour event, dating back to the final two tournaments of last season.
Overnight leader Tim Herron and Chris DiMarco were in contention deep down the stretch, but both met a jagged demise.
DiMarco (70) made double bogey at 14 after hitting his approach shot into the rocks, while Herron (75) made quadruple bogey at 16 after doing the same.
They tied for third at 26-under.
Herron, who started the day with a four-shot lead, played the front side in 2-over 38. Meanwhile, Haas shot 4-under 32 ' the best front-nine score by anyone in the field on Sunday.
Haas made a 15-foot eagle from the fringe at the par-5 sixth to leapfrog Herron on the leaderboard.
And despite a couple of bumps early on the back, he never fully relinquished his position at the top ' until the final hole.
Haas three-putt bogeyed the 10th and 13th holes, but still led DiMarco and Weir by a shot, at 28-under. Herron was two back after bogeys on 12 and 13.
DiMarcos run ended at the par-5 14th. He lost a 4-iron from 230 yards into the desert rocks. He took a penalty stroke and eventually made 7.
With DiMarco out of the picture, Herron climbed back in. He flew a 6-iron from 212 yards within eight feet of the hole at 14. He converted the eagle to tie Haas, who like Weir parred the 14th, for the lead.
Herrons chance to win his first tournament since the 1999 Bay Hill Invitational came to a conclusion at the par-4 16th. After hitting his tee shot into the left fairway bunker, he flew his 88-yard approach shot over the green and into a crevice between two rocks.
With the option of taking a penalty drop in the crude elevated area or replaying from the fairway bunker, he chose the former.
Herron removed several loose impediments before dropping into a patch of dirt. He then bladed his next shot into the canal running parallel to the green, and made quadruple-bogey-8.
After the lengthy wait, Weir made a seven-footer for birdie at 16 to very briefly tie Haas at 28-under. Haas also made birdie, from a foot closer, to maintain his tenuous one-stroke advantage.
Haas almost chipped in to match Weir's birdie at 17. His error at the last cost him his 10th career tour win. He won once in the 1970s, six times in the '80s and twice in the '90s. His last victory was the 1993 Texas Open.
'I'll look back, I guess, on the redeye tonight and think about what could have been,' he said.