Overnight leader Padraig Harrington was joined at the top of the leaderboard by Tim Clark as the pace-setters played their third rounds at the World Golf Championships-Bridgestone Invitational in Ohio.
Ireland's Harrington began the day at seven under par, one shot clear of South Africa's Clark and quickly stretched his lead to two shots after pitching from 110 yards to inside ten feet as Clark slashed out of right rough to 30 feet, from where he two putted the first hole for par.
Harrington sank the birdie putt and moved to eight under in overcast conditions at the Firestone Country Club's par 70, 7,400 yard South Course.
American Scot Verplank had joined Clark at six under with a birdie at the par five second but immediately gave back a shot with a bogey at the par four third.
Clark, though, birdied the second and the third as Harrington parred and he drew level with the Irishman at eight under.
Also on five under as the tournament front-runners negotiated the front nine were American Steve Stricker, having played three holes and Thailand's Prayad Marksaeng, both of whom birdied the second.
Harrington appeared to be in trouble at the second when he drove into left rough at the second but he got a drop and from the new lie successfully found the fairway from where he got up and down for a par five.
Clark followed the trend and birdied the same hole to get to seven under, cutting Harrington's lead to one shot but the Irishman was looking confident as he strode to the third.
Spain's Miguel Angel Jiménez was four under par for the tournament with two holes to play, on the same mark as Masters Tournament champion Angel Cabrera of Argentina, who had played nine holes, Robert Allenby of Australia, after six, and American Chad Campbell, who had played 12.
American Ryder Cup star JB Holmes moved into contention at three under thanks to an early 65, alongside Valhalla team-mate Kenny Perry, who had two to play, World Number One and six time winner Tiger Woods, who went out in 34, US Open champion Lucas Glover, Open Championship winner Stewart Cink and Spain's Alvaro Quiros.
Woods began steadily with four straight pars before a birdie at the par three fifth was followed by bogey, birdie at the eighth and ninth.
Ian Poulter was getting his tournament back on track having undone an opening 67 with a 74 on Friday that sent him back to one over par at halfway.
The Englishman progressed to two under with a third round, four birdie, one bogey 67 and compatriot Oliver Wilson was also at the same mark after eight holes having chipped in from the rough above a greenside bunker at the first for birdie before a bogey at the six sent him back to two under.
Rain had fallen briefly at Firestone for the first time in the tournament, about an hour before Harrington had teed off, with thunderstorms also forecast for later in the day and showers returning as the leaders played the fourth.
Jiménez closed bogey, birdie for a 66 to finish his third round at four under par, which was looking a very good score as bogeys started to litter the cards of the players in front of him.
Harrington and Clark both bogeyed the par four fourth, while Verplank continued to drop shots with bogeys at the fourth and par four sixth.
Marksaeng was also in trouble, bogeying the fifth and sixth to drop to three under alongside Verplank, while Kenny Perry reached four under thanks to a 66.
Harrington and Clark dropped to seven under and saw their lead extended to three shots over the field, Jiménez and Perry in the clubhouse at four under alongside the still playing Chad Campbell, Glover, Cabrera, Quiros and Stricker.
Clark then birdied the par three seventh to move into the outright lead at eight under as Harrington parred, but the South African wiped his advantage out with a bogey at the ninth as they both made the turn at seven under par.
Stricker birdied the eighth and Jerry Kelly sank birdies at eight and nine as both moved to five under.
Woods came alive on the closing stretch, birdies at the 13th and 15th moving the six-time Firestone winner to five under also, ominously close to the lead.