Jimmy Walker overcame a few wild tee shots with four birdies on the back nine for a 2-under 68 and a one-shot lead over defending champion Jason Day going into the final round of the rain-plagued PGA Championship.

This already was shaping up as a major like no other.

Even as Walker and Day were finishing their rounds, the fourth round already had begun on rain-soaked Baltusrol. The PGA of America chose not to redo pairings for the final round because it was the only chance to finish by Sunday.

Then, the PGA decided to play preferred lies for the final round, which had not happened in a major in more than a half-century. That means players will be able to lift, clean and place their balls anywhere but the rough.

Walker, who was at 11-under 199, was among 10 players who didn't even hit a shot Saturday because of storms that flooded the Lower Course at Baltusrol. He had never contended in a major until this week, and went into the final 18 holes having been at least tied for the lead all three rounds.

"I made a couple of tentative swings early," Walker said. "I just said, 'Trust it man, you're swinging it good. Keep the pedal down.'"

The final round figured to be the toughest, especially with the cast of characters behind him.

Day surged into the lead with a 75-foot birdie putt on No. 7 from the front to the back of the green, and a tee shot to 4 feet on the par-3 ninth. Walker and Robert Streb, who shot a 63 on Friday to share the 36-hole lead, began to struggle off the tee and on the green, both dropping two shots behind Day at one point.

Day settled into a string of pars on the easier back nine until finishing with a birdie for a 67. It was his seventh straight round of 68 or better in the PGA Championship.

"I went a stretch of eight holes without a birdie and I needed one to get some motivation for the fourth round," Day said. "But I played some nice golf out there."

He is trying to join Tiger Woods as the only players to win the PGA Championship in consecutive years since it went to stroke play in 1958.

"It would be really nice to get that second major under my belt," Day said. "I don't want to win just one for my career."

Unlike the British Open two weeks ago, this is hardly a two-man race.

Henrik Stenson, who won the duel at Royal Troon with a record score in a major, piled up enough birdies on the back nine for a 67 and was two shots behind in his bid to join Ben Hogan as the only players to win back-to-back majors at age 40.

Brooks Koepka, playing for the first time since the U.S. Open because of an ankle injury, had a bogey-free 66 and was two shots behind. A big week by Koepka could all but clinch a spot on his first Ryder Cup team.

Streb, meanwhile, didn't make his first birdie until the 17th hole, only to three-putt from just inside 8 feet for bogey on the 18th and a 72. He was four shots behind, along with William McGirt (66) and Hideki Matsuyama (67).

Jordan Spieth finished with eight straight pars, missing good birdie chances along the way, and had to settle for a 69. That left him seven shots behind, which would require a record-tying comeback at the PGA Championship to have any chance.

Patrick Reed also wasted a good opportunity, making double bogey on the sixth hole and shooting 70 to finish six shots behind.

The PGA Championship was trying to avoid its second straight Monday finish at Baltusrol. Phil Mickelson won on a Monday in 2005. Rain began to fall as the leaders finished the third round, though play kept going. Any stoppage in play was sure to mean one more day before the Wanamaker Trophy is handed out.