Watney made eight birdies and two bogeys in a superb round of 66 to head into the final day leading at 13-under-par 203 after a perfect sunny afternoon on the shores of Lake Michigan that proved ideal for low scoring.
More than 50 players finished under par with nine within five strokes of Watney and each of the top six chasing their first majors, setting the stage for a dramatic finale to the last major of the year.
“There’s some really good players that haven’t won a major,” Watney said. “You’ve got to start somewhere and hopefully tomorrow will be my day.
“At this point it’s just another golf tournament. I think that’s the best way for me to look at it. Obviously it’s not but I just need to go out there and keep doing what I’m doing.”
Briton Rory McIlroy underlined his reputation as one of the top emerging players in world golf with a 67 to end the round at 10 under, tied for second with big-hitting American Dustin Johnson (67).
The 21-year-old Northern Irishman is playing in just his ninth major but has twice finished tied for third, at last year’s PGA and this year’s British Open.
“I definitely have a chance,” he said. “But there’s so many other great players on the leaderboard as well, someone’s going to have to go out there and shoot a good score.
“I’m in contention in a major and it’s a great place to be.”
Johnson is also bubbling with excitement despite leading this year’s US Open at Pebble Beach by three shots at the start of the last day only to crumble under the pressure and shoot an 82.
China’s Liang Wenchong shot a flawless round of eight under 64 to better the course record jointly held by Darren Clarke and Miguel-Angel Jimenez and join Australia’s Jason Day (66) and Germany’s Martin Kaymer (67) at nine under.
Australia’s Steve Elkington, who won the PGA Championship 15 years ago, wound back the clock to reach eight under and join the American trio of Jim Furyk (70), Zach Johnson (69) and Jason Dufner (69).
Tiger Woods birdied his last two holes to end an exhausting day tied for 31st at three under as his hopes faded of ending a year dominated by revelations about his private life on a high.
The world No. 1 played the last 12 holes of his uncompleted second round in the morning then returned after lunch to play his third round and said he was satisfied his game was heading in the right direction despite not winning a tournament this year.
“I feel so much better, how I’m hitting the golf ball now,” he said. ” The striking, the sound, the feel, more than anything, it feels good.”
The perfect weather conditions also allowed tournament officials to get the championship back on schedule after nearly six hours were lost on the first two days because of heavy morning fog.
The third round was played in groups of three off split tees because of the delays to the second round, which American Matt Kuchar eventually led by a shot from Watney, but will revert to pairs on Sunday.
Kuchar ended the day six shots off the pace at seven under after a 73 in the third round.
The winners of this year’s last two majors, British Open champion Louis Oosthuizen and US Open winner Graeme McDowell, both missed the cut.
Last year’s PGA winner, South Korean Yang Yong-eun, also made an early exit, along with the 2008 champion Padraig Harrington, who double-bogeyed the last hole to jeopardise his chances of making the European Ryder Cup team.
“I have done everything I can now, and there is nothing more I can do,” Harrington said. “My majors have been poor this year but everything else has been good.”
