* Woods cards 68 to maintain seven-shot lead
* Will be chasing record eighth Firestone title
* Swede Stenson alone in second after 67
Tiger Woods failed to replicate the sizzling form he produced on Friday but remained in imperious command with a seven-shot lead after Saturday's third round at the WGC-Bridgestone Invitational.
In pursuit of his fifth PGA Tour victory of the season, Woods "grinded" out a two-under-par 68 on a warm, breezy day at Firestone Country Club to maintain his overnight lead.
The American world number one, winner of a record seven World Golf Championships (WGC) titles here, struggled at times for accuracy off the tee as he mixed five birdies with three bogeys for a 15-under total of 195.
Woods had distanced himself from the field with a stunning 61 on Friday and will head into Sunday's final round with an intimidating record, having triumphed 52 of 56 times on the PGA Tour when holding at least a share of the 54-hole lead.
"I feel pretty good," the 14-times major champion told reporters. "Today was a day that I didn't quite have it, but I scored. And that's the name of the game is posting a number, and I did today. I grinded my way around that golf course.
"It was playing a little blustery. As smooth as yesterday was, as difficult as today was, it's just one of those things where I was just trying to build on my lead somehow. And for most of the day I was doing that.
"Ended up being a dead push for the day, but that's not too bad, either. Hopefully I can seal the deal tomorrow and get ready for the PGA (Championship) at Oak Hill," he added, referring to the year's final major next week.
Woods' closest challenger going into the final round is Swede Henrik Stenson, who fired a 67 to leave him at eight under.
"I'm just going to try and play my game, and I'm excited to go out and play with him tomorrow (in the final pairing)," said Stenson. "He's obviously playing great, and it'll be a good test, a good measurement.
"We might just be there for watching the final victory lap. We'll see tomorrow. But I can only do so much. I can play my game and see where that takes me."
Jason Dufner, who birdied his first four holes on the way to a 67, was alone in third at seven under, a stroke better than fellow American Bill Haas (69) and Englishmen Luke Donald (68) and Chris Wood (70).
British Open champion Phil Mickelson, who by his own admission struggled for focus in his opening round, carded a 67 to finish at even-par 210, level with U.S. Open winner Justin Rose (69) and world number three Rory McIlroy (69) among others.
Woods made an ideal start, hitting a superb approach to 12 feet above the hole at the par-four first and coolly sinking the birdie putt.
He also birdied the par-five second after reaching the green in two and two-putting but his lead slipped back to seven when playing partner Keegan Bradley drained a 40-foot eagle putt.
Woods parred the next six holes before bogeying the ninth after hitting his tee shot into a poor lie in a fairway bunker from where he could advance his second shot only 87 yards.
After hitting his approach to nine feet, he missed the par putt to end a run of 37 consecutive holes without a bogey, reaching the turn in one-under 34 with a seven-stroke lead.
However Woods immediately recovered, sinking an eight-footer to birdie the 10th and regain an eight-stroke cushion at 15 under.
Another birdie followed in unexpected fashion at the par-four 13th where he chipped in from an uphill lie in thick rough below the green, his ball popping up before tracking toward the cup some 40 feet away.
Woods failed to capitalise, though, as he recorded bogeys at the par-four 14th and the par-five 16th after finding fairway bunkers off the tee on both holes.
He birdied the par-four 17th, sinking a curling eight-footer to regain a seven-stroke advantage, and salvaged par at the last, despite missing his sixth fairway of the day off the tee.
Woods has dominated the elite WGC events since they were introduced in 1999, winning 17 of them in 41 starts.