'It didn't look good when I knocked it out of bounds on No. 10, but then I holed one from a bunker on 11 after chipping in on the front nine too,' said Haas, who picked up $240,000 for the win. 'I was good around the greens today. That's where I made most of my birdies.'
Mark James posted a 5-under 67, while Tom Kite shot 68 to share second place at 9-under-par 207. David Edwards was two strokes further back at minus-7 after a 71. Tom Jenkins rounded out the top five at six-under-par 210 after a closing 69.
Overnight-leader Bruce Fleisher struggled to a 2-over 74 to end in a tie for sixth at minus-5. He had won 12 of the previous 16 times he had led entering the final round. Fleisher ended alongside 2003 champion Hale Irwin (68) and Bruce Lietzke (66) in sixth place at The Hills Country Club.
Haas flew up the leaderboard with a stellar front nine. He opened with a birdie on the par-5 second. The 52-year-old came right back to birdie the par-3 third from three feet out.
He kept rolling with a birdie on the fourth, then sank a 10-footer for birdie at the fifth to move to 8 under. Haas capped a run of five straight birdies as he chipped in for birdie at the sixth.
Haas got to 10 under with a birdie at the eighth. However, he stumbled to back-to-back bogeys from the ninth to slide back to 8 under, three behind Fleisher.
The four-time winner on the Champions Tour got one stroke back with birdie on the 11th, where he holed out from a greenside bunker.
Haas gave that shot back as he bogeyed the 14th, but was just two back as Fleisher faltered on the back nine.
He came right back to birdie 15 from 17 feet away, then sank an 15-footer for birdie at 16 to grab a one-stroke lead over James, Kite and Fleisher.
Haas, playing two groups ahead of the leaders, got up and down for birdie on the 18th to close at minus-11.
'I felt good starting out and I knew I needed to get some things going early,' Haas admitted. 'I had a lot of good shots today.'
Haas did all this as his back was acting up throughout the round.
'My back started to bother me at 18 yesterday, I took about 10 advils today,' stated Haas. 'My back flares up every now and then.'
James played alongside Haas and posted three birdies on the front nine, then two more on the back to get to 9 under.
Kite, playing in the penultimate group, birdied the fourth and sixth. He eagled No. 8 to jump to minus-9. However, he could only par the final 10 holes to end two back.
'It was a good day, but it could have been better,' Kite admitted. 'I left a lot of opportunities out there.'
Fleisher was in control thanks to birdies at one, two, four and six. That got him to 11-under par. However, things fell apart for the 57-year-old on the back nine.
The 18-time winner on the Champions Tour bogeyed the 11th as his lead slipped to one. Fleisher was unable to save par from a greenside bunker at 14 and dropped into a tie for the lead with Kite, James and Haas.
Fleisher kept fading with a bogey on 15. He then double bogeyed the 16th and bogeyed 17 to end six back.
Don Pooley closed with a 3-under 69 to share ninth place with Bob Gilder (72) at 4-under-par 212. Brad Bryant, Ben Crenshaw, Pat McGowan, Des Smyth, Craig Stadler and D.A. Weibring were one stroke further back at minus-3.