Left-hander Watson moved to 17-under for the tournament with England’s Justin Rose, who shot a 69, and American Keegan Bradley, who made 66, tied for second at 14-under.
Watson’s round included three bogeys and six birdies after he started with an eagle on the par-five first hole.
“I’ve just got to do what I have been doing. Obviously you look at pin locations and so the driver might not come out as much,” Watson said, looking ahead to the final round.
Despite already having three PGA Tour wins to his name, Watson said he was nervous about chasing his first WGC win.
“If anybody says they are not nervous going into Sunday with the lead or a chance to win it, they are just lying to you. Their psychologist is telling them to lie themselves,” he quipped.
“I’m nervous, I’m going out and I’m trying to beat this golf course. I’m trying to man up and make a good score.”
Rose, who also has yet to win in the elite series, ended his round with a disappointing three putt for bogey on the 18th.
“Obviously three back, it’s a lot to Bubba on this golf course, he seems to make birdies pretty easily out here,” said Rose.
“But...there is only one guy at 17 under and the rest of the pack is right there so it doesn’t take much. If he has an average day it’s there for the taking.”
Bradley, the PGA Championship winner last year, had a bogey free round and heads into Sunday full of confidence.
“It feels so good to play good golf like that. I never got myself into trouble and my chipping, most importantly this week, has been so good.
“I’m taking care of the par fives which is what you always have to do on this course. I just feel really comfortable out here,” he said.
Tiger Woods (68) and Northern Ireland’s Rory McIlroy (65) both moved up the leaderboard and ended the day eight shots behind Watson, tied for eighth.
McIlroy shot a superb six-under 30 on the front nine, despite not gaining a stroke on either of the two par fives, but then made bogeys on the 14th and 16th holes, both par fours, to end with a seven-under round.
“The bogey on the 14th really stopped my momentum, I just couldn’t get it back after that,” he said.
Woods was in great touch on the first seven holes but a bogey on the eighth stalled his charge.
The 14-time major winner hit his second shot over the green on the 531-yard par-5, then found the greenside bunker before two-putting for a bogey.
Australian Adam Scott, who had been third overnight, saw his bid fall apart on the last three holes when he made two bogeys and a double when he drove into the water on the 18th.
Dane Peter Hanson was in fourth place, five shots off the lead after a 69.
McNeill grabs lead in Puerto Rico
In Rio Grande, Puerto Rico, American George McNeill shot a five-under par 67 on Saturday to snatch a one stroke lead after the third round of the Puerto Rico Open.
Sweden’s Henrik Stenson, who finished with consecutive birdies, was tied for second with American Kevin Stadler, after both carded 66.
Australia’s Matt Jones, who led by three shots overnight, fell back to fourth place, two shots behind McNeil, after an even par round of 72.
Japan’s Ryo Ishikawa remained in the frame, just three strokes off the lead, after shooting a 69.
McNeill eagled the par-five third hole but dropped shots with bogeys at the seventh and eighth holes before covering the back nine in four-under par.
