Overnight leader Padraig Harrington shot a 69 to maintain his clubhouse advantage as the late wave of starters began their second rounds at the World Golf Championships-Bridgestone Invitational in Ohio.
Three time Major winner Harrington had produced his best round of the year when he posted a bogey free six under par 64 at Firestone Country Club to take a two shot opening round lead over Thailand's Prayad Marksaeng, Tim Clark of South Africa and American Scott Verplank.
The Irishman picked up where he left off, moving to seven under par after five holes having birdied the par five second when he shot out of right rough from 71 yards to six feet from the hole.
Harrington bogeyed the par four eighth, the only blemish on his round, but rebounded at the par four 13th courtesy of a successful 30 foot birdie putt that sent him back to seven under, the Dubliner making par all the way home from there.
"Shooting that score yesterday gave me a great chance for the tournament," said Harrington. "Anything under 70 from here on in is going forward so I'm quite pleased to have shot 69."
Verplank matched playing partner Harrington with a 69 that left him five under while Marksaeng, part of the late wave of starters, got his second round under way with birdies at the second, fifth and seventh holes to join Harrington at seven under.
Clark, also drawn to start in the later wave in a field reduced to 79 players following the withdrawal through injury of Paul Casey, birdied his second to get to five under on the back nine after four holes.
Spain's Alvaro Quiros made a big move into contention with a 65 to jump from two over to three under, while Woody Austin was also on three under following a 68, as was former Masters Tournament champion Zach Johnson, who bogeyed his last hole, the ninth, to end with a level par 70.
World Number One Tiger Woods, a six-time winner at Firestone, was another early starter and came off with a par round of 70 to stay at two under, while playing partner Sergio Garcia of Spain carded a two over 72 to fall to level par.
Four birdies in his first 12 holes moved England's Oliver Wilson to five under par for the week but bogeys on his back nine at the fourth, eighth and ninth left The Ryder Cup player with a 69, two under for the week.