Tom Kite is alone in second place after a 5-under-par 67 at Sonoma Golf Club. Craig Stadler, who has not won since the SAS Championship in 2004, and Bob Gilder are knotted in third place at minus-4.
Jay Haas and Loren Roberts are the only two players left with a chance to win the money title and the Charles Schwab Cup and its $1 million annuity. Haas has a slight lead in both races with this final event.
Haas has the lead this week over the No. 2 player on the tour. Haas shot a 2-under 70 and is tied for eighth place while Roberts only managed a 1-under 71.
'Overall, I'm happy with the start,' said Haas. 'Neither one of us looks for confrontation or anything like that. We're pretty low-key guys. It's just fun being in that position.'
For the moment, the two contenders for Player of the Year have to catch the 15th-leading money earner on the Champions Tour in 2006.
Thorpe broke into red figures quickly when he holed a wedge shot from 70 yards out for an eagle at the par-5 second hole. He added back-to-back birdies at five and six, but dropped a shot at the par-3 seventh.
Thorpe, who won this title in 2003, more than atoned for the error at the seventh. He once again rattled off two consecutive birdies, this time from the eighth.
He was 5 under par for the championship, but got to minus-6 at the par-5 13th. Thorpe holed a long birdie putt there, then got up and down for par from a bunker at 14.
Thorpe bogeyed the 15th hole to fall back to 5 under par, but things looked like they were going to get worse at the par-5 16th. He drained a 25-foot par putt to stay at minus-5.
Thorpe sank an 8-foot birdie putt at the par-3 17th to move into sole possession of the lead. He parred the closing hole to stay one in front of Kite.
'Today we kept our patience out there,' said Thorpe. 'I hit a couple of crooked shots out there today. You can't miss a fairway. If you miss a fairway, you're dead. We hit fairways pretty good and the holes I did miss, I managed to hustle the ball pretty good.'
Thorpe has earned $856,784 so far this season and has collected four top-10s. He finished as the runner-up to Bobby Wadkins at the Ford Senior Players Championship, but is not completely satisfied with the year.
'I worked very, very hard this year,' admitted Thorpe. 'It hasn't been a bad year, but we haven't gotten to the winner's circle yet this year. It's a feather in your cap because you're competing against the best that ever did it.'
Kite also got his round going with an eagle as he holed out a lob wedge shot from 57 yards at the ninth. He kicked in a short birdie putt at the 10th, then holed out another wedge shot for eagle, this time at the 11th.
'When you play those three holes and you have one putt and the one putt is a two-footer, that's kind of strange,' said Kite. 'That doesn't happen very often.'
Kite missed a 6-footer for par at the 12th, but a 30-foot birdie putt at the last got him within one of the lead.
Lonnie Nielsen, Andy Bean and Des Smyth are tied for fifth place at 3-under-par 69.
Haas was joined in eighth place by Bruce Lietzke, Hale Irwin, Tom Purtzer, Scott Simpson and defending champion and three-time winner Tom Watson.