The two-time Michelob champion is tied with Billy Mayfair at 9-under-par 133. The two are one shot clear of overnight co-leader Hidemichi Tanaka (70).
Charles Howell III (65) leads a group of six at 7-under. Last weeks winner Loren Roberts (69), Corey Pavin (69), Peter Jacobsen (68), Jose Coceres (69) and Brandt Jobe (68) all share fourth place.
Duval started his day with back-to-back bogeys on 10 and 11. He birdied 15 and 16 to get back to even par for the day.
The first couple of holes, really only hit one bad shot and made two bogeys, Duval said. After that, just kind of hung in there. I had a chance to turn under par, but failed to make the putt on 18.
Duval atoned with a birdie at the first and added another at the third. He then went bogey-birdie-bogey-birdie over his next four holes.
I played pretty solid. The only problem I had was just kind of just missing most of my fairways, said Duval, who hit six of 14 fairways Friday.
While Duval is seeking his first win since the 2001 British Open, Mayfair is looking for his first since the 1998 Buick Open. Hes only notched a pair of top-10s this season; however, one came in a tie for fifth at the U.S. Open.
Obviously, the U.S. Open was the highlight of my season, said Mayfair, who is 87th on the money list. Usually when Im having a bad season its because of my putting, but this year its been because of my iron play. Ive been driving the ball pretty good, but havent been hitting enough iron shots close to make a lot of birdies.
That wasnt a problem Friday. Mayfair hit 16 of 18 greens in regulation and made eight birdies without a bogey.
Howell made seven birdies and a bogey in round two. The tour sophomore is searching for his first tour title. But with a good finish this week ' with or without trophy in hand ' Howell can achieve one of his 2002 objectives.
The Tour Championship was one of my main goals starting the year off, said Howell, who is currently 37th on the money list. Im going to play the rest of the year out.
The 23-year-old Augusta, Ga., native narrowly missed a spot in last years Tour Championship field. He needed to finish in the top five the week before, but finished tied for 12th.
Two-time defending champion David Toms (70-71) barely made the cut. He finished on the number, at 1-under-par 141.
Full-field scores from the Michelob Championship