Cook, the Administaff Small Business Classic winner two weeks ago in Texas, had a 19-under 197 total on the Sonoma Golf Club course, the best 54-hole score in a 72-hole tournament since Jack Nicklaus also had a 197 total in the 1990 Senior Players Championship. Cook tournament-record 62 on Friday.

The six-stroke lead is the largest after three rounds on the Champions Tour since Jay Haas had a six-stroke lead in the 2005 Schwab Cup Championship.

Russ Cochran (68) was second at 13 under. Tom Watson (71), who began the day four shots behind Cook, and Brad Bryant (69) were 12 under.

Season points leader Loren Roberts had the day's best round with a 66 to move to 7 under. Roberts struggled the first two rounds but had seven birdies and one bogey to jump up 10 spots to 15th place. Third-place Bernhard Langer (70) was 9 under, 2008 points champ Haas (70) was tied with Roberts at 7 under, while Fred Funk, who went into the weekend 165 points out of the lead, was 2 under following a 74.

The season points winner will receive a $1 million annuity.

Unlike a day earlier when Cook needed just 23 putts in his 62, he had to scramble on a few holes. He bogeyed the 427-yard, par-4 12th, came back with birdies on 13, 15 and 16 then made an 8-foot putt to save par on the 18th.

Watson couldn't sustain the momentum he built after making eight birdies on Saturday. The 60-year-old Hall of Famer bogeyed the first hole and struggled with his touch most of the afternoon.

That enabled Cochran to make his move. One of only three players to break 70 in each of the first three rounds along with Cook and Bryant, Cochran had six birdies and shook off a pair of bogeys to slip into second place.

Langer looked as if he might make a stronger run at Roberts, getting to 10 under after a birdie on the 417-yard, par-4 sixth, but had consecutive bogeys on 7 and 8, dropped another stroke on the 18th.

Joey Sindelar withdrew and was taken to a hospital after complaining of dizziness and shortness of breath. According to a Champions Tour spokesman, Sindelar became dizzy after playing the 204-yard, par-3 fourth hole.

Sindelar rested in between holes and tried to play the fifth before withdrawing. Medical personnel attended to Sindelar at the course and the 51-year-old player was taken to a hospital for further tests. Sindelar, a seven-time winner on the PGA Tour titles, was 7 under for the tournament before withdrawing.