Since Tiger Woods missed his first cut on tour since 1998, Singh had an opportunity to reclaim the No. 1 spot in the World Ranking. Singh needed to finish better than a solo third, so the three-time major winner will have to wait for No. 1 until he returns to the tour after a trip to Fiji.
With all of the talk about Singh and his fellow members of the 'Big Five' in the field, it was Purdy, a 31-year-old, three-year member of the tour that hoisted the trophy.
Purdy began the final round two shots behind O'Hair and broke into red figures with a birdie at the third. He drained a 30-footer for birdie at No. 6, then added a 35-footer at the eighth to go ahead by two.
O'Hair, 22, bogeyed the third hole, but drew even with Purdy. At the par-5 seventh, O'Hair two-putted from 45 feet for birdie and at eight, he sank a 10-footer for birdie.
O'Hair came up short of the green with an 8-iron at the ninth, but chipped up to 4 feet. He missed the par putt to fall one behind and Purdy extended the advantage with a 5-foot birdie putt at the 11th. O'Hair holed a clutch 10-footer for par at the 10th to stay within two.
At the par-3 13th, O'Hair hit a 6-iron inside 4feet to set up birdie. The deficit was only one for O'Hair, but an 8-iron approach at 14 sailed over the green into a bunker. He blasted out to 10 feet, but hammered the putt almost 4 feet from the cup. O'Hair converted the bogey putt to fall two down.
Purdy landed on the back fringe in two at the par-5 16th and lagged his eagle try to 3 feet. He sank the birdie putt to grab a three-shot advantage, but O'Hair would stay in the hunt. At the same hole, O'Hair sprayed his second right of the green and pitched 15 feet past the hole. He drained the birdie putt to cut the margin to two.
Purdy played solidly down the stretch. He hit safe shots to the centers of the 17th and 18th greens, and two-putted for pars.
O'Hair had to be more aggressive and hit his tee ball to 18 feet at the par-3 17th. He missed the putt and had to hole out at the closing hole to force a playoff. O'Hair split the fairway, but his pitching-wedge came to rest 15 feet from the hole. He rolled in the birdie putt to lose by only one.
'Today I played my heart out,' said O'Hair. 'I'm proud of myself and really happy for Ted. I learned what it takes to win out here. I made too many bogeys today, but I realized this week that I'm good enough to win.'
Instead, it was Purdy who collected his first PGA Tour victory. He became the fifth first-time winner on tour in 2005 and did not make a bogey in the final 27 holes of the tournament.
'It hasn't sunk in yet. I played flawless today,' admitted Purdy, who pocketed $1,116,000 for the win. 'I learned a lot today. I let go of any desires to win and let it happen.'
Purdy finally made it to the winner's circle after two heartbreaks last year. He squandered a four-shot lead at the Heritage, then lost a five-hole playoff to Stewart Cink. Purdy had a 3-footer on the 72nd hole of the B.C. Open to force a playoff with Jonathan Byrd, but missed.
'It's such a great game,' said Purdy. 'I won on the PGA Tour and that's been my dream my whole life.'
Nick Price (67), Scott Verplank (70), Shigeki Maruyama (68) and Omar Uresti (66) tied for sixth place at 10-under-par 270.
Ernie Els, third in the world ranking, shot a 4-under 66 and shared 10th with Mark Brooks (66), J.J. Henry (68) and Jaxon Brigman (69). The group came in at minus-9.
Reigning British Open champion Todd Hamilton was one shot back heading into the final round, but struggled to a 4-over 74. He tied for 18th place at 7-under-par 273.