A 69 from Padraig Harrington kept the field at bay as the Irishman maintained his lead after the second round of the World Golf Championships-Bridgestone Invitational.
Three time Major winner Harrington had produced his best round of the year with a 64 at Firestone on Thursday to lead by two from Thailand's Prayad Marksaeng, Tim Clark of South Africa and American Scott Verplank.
The Irishman picked up where he left off as he began his second round well, moving to seven under par after five holes.
He bogeyed the par four eighth, the only blemish on his round, but rebounded at the 13th courtesy of a birdie from 30 feet.
"Shooting that score yesterday gave me a great chance for the tournament," Harrington said.
"Anything under 70 from here on in is going forward so I'm quite pleased to have shot 69."
The Dubliner admitted his second round had been less aggressive than his first but added: "I normally play the first rounds cautiously. I was a bit cautious today. I was more worried about my misses rather than having that sort of confident attitude and going after a few more pins.
"You know that if you short side yourself you're going to have difficulty getting up and down. But you've got to make some birdies. My short game has been good enough, so I probably should be a little bit more aggressive over the weekend."
Harrington will take a one shot lead into the third round on Saturday, with Clark on six under following a 68.
“Obviously happy with that score,” said the South African. “The course firmed up quite a bit, and particularly in the afternoon the greens were pretty firm, so tougher to score. Less birdies, but also less bogeys today, so overall happy with two under in these conditions.”
Verplank matched Harrington with a 69 that left him at five under while Marksaeng moved into a share of the lead at seven under before falling off the pace on the way to a 70 which left him at four under.
Also four under are Americans Steve Stricker, who carded a 69, and Jerry Kelly, who hit a 65.
In a field reduced to 79 players following the withdrawal through injury of Paul Casey during the first round, Spain's Alvaro Quiros made a big move into contention with a 65 to move from two over to three under.
American Woody Austin was also on three under following a 68, as was former Masters Tournament champion Zach Johnson.
World Number One Tiger Woods, a six time winner at Firestone, returned a 70 to stay at two under par, while playing partner Sergio Garcia carded a 72 to fall back to level par.
Four birdies in his first 12 holes moved England's Oliver Wilson to five under par for the week but three bogeys on his back nine left The Ryder Cup player with a 69, two under for the tournament.
Open Championship winner Stewart Cink and US Open Championship winner Lucas Glover also finished two under.
World Number Two Phil Mickelson added a 69 to his opening 70 while English duo Nick Dougherty and Lee Westwood both shot 71 to move to level par.
Northern Ireland's Darren Clarke, the 2003 champion, will start round three at one over following a 70.