David Frost shot 64, missing a short putt on the 18th hole. Fred Couples was third at 65, and Mark O'Meara had a 66. Bernhard Langer, Steve Elkington and Duffy Waldorf shot 67.
Charles Schwab Cup points leader Kenny Perry topped the group at 68. Perry entered the event 612 points ahead of second-place Langer. If Langer wins the tournament, Perry needs only to finish fifth or better take the season title and $1 million annuity.
Senior shot a 6-under 30 on the front nine, culminating with an eagle on the ninth hole. He birdied Nos. 11 and 12 and allowed himself to start thinking big.
"I started counting the easy holes that I could possibly birdie," he said. "As soon as I thought that, I made a bogey." ''
Frost has two victories season, including his first senior major victory at the Regions Tradition in June.
Couples is dealing with neck and back issues. He had a double bogey on the eighth hole.
Couples had nine birdies, three immediately before his double bogey and two immediately following.