SPRINGFIELD, N.J. — Jason Day seemingly wanted to temper his expectations in defense of his P.G.A. Championship title. He was worn out after playing the Canadian Open last week, a week after the Open Championship at Royal Troon. He also caught a cold from one of his young children.
To make matters worse, Day’s wife, Ellie, suffered an allergic reaction at the P.G.A. Champions dinner Tuesday night, forcing the couple to spend most of the night in a nearby hospital.
“We were there until two o’clock or something like that,” Day said. “So I’m kind of running on E right now.”
Day had arrived at Baltusrol Golf Club having never seen the course, and he squeezed in only one practice round, on Wednesday. But the world’s No. 1 did not play like someone who was unprepared by Thursday, when he posted a two-under-par 68 in the opening round, putting him in a tie for ninth, three strokes behind the leader, Jimmy Walker, who shot 65 to tie his best round in a major.
“I’m very excited about how I hit it today,” Day said. “To be able to go out there and see the shot do what I need it to do was exciting for me. Really positive stuff going into the next three rounds.”
After the first three majors were claimed by first-time winners, Day has put himself in position to be the first player since Tiger Woods in 2006 and 2007 to win the P.G.A. Championship back to back.
Ahead of him, three players — Emiliano Grillo, Ross Fisher and Martin Kaymer — stand at four-under par. Four others, including Henrik Stenson, whose torrid play continued after winning the British Open, finished at three-under par.
On a suffocating afternoon with dense heat, volatile winds and the threat of late afternoon storms, scores were held in check as the day wore on.
Jordan Spieth continued to struggle off the tee, but he ground out an even-par 70 after making birdie on two of his last three holes.
Two inches of rain Monday night softened the course for the practice rounds on Tuesday and Wednesday, but by Thursday afternoon the fairways and greens had grown firmer under a relentless sun, making long approach shots on the sizable par-4s difficult to control.
“I think definitely it was harder in the afternoon,” said Russell Henley, who posted a two-under. “Got a little bit — I’m not going to say baked out, but just a little bit firmer.”
The heat also took its physical toll. Many players tried to limit their practicing during the week by not playing a full round to conserve energy. In some ways, Day said he might have benefited by arriving late and feeling too ill to practice.
“By Thursday, if you practice Monday, Tuesday, Wednesday, you could be pretty tired with how hot it was,” Day said. “I’m glad I took Monday, Tuesday off, even though I’m a bit under the weather. It was kind of a blessing really.”
The dry fairways convinced some players to put away their drivers and tee off more safely with 3-woods or even irons. Day used a 3-iron off the tee at the 550-yard par-5 18th and followed that with a 4-iron approach that wound up in a front greenside bunker.
“If you don’t need to take it on, you don’t need to,” Day said.
Baltusrol has only two par-5s — the 17th and 18th holes — but its long par-4s put a premium on strong mid-iron play and accuracy off the tee because of the length of the rough.
“If you are not driving the ball well, it’s going to be hard to score,” said Rickie Fowler, who also shot two-under par. “You have got to be playing out of the fairway.”
After making par on his first seven holes, Spieth drove his ball way right on the eighth and had to pitch out from underneath a pine tree. His rescue shot did not reach the fairway, and his approach landed at least 80 feet from the hole. He wound up three-putting for a double bogey.
Spieth’s frustration simmered throughout the round until he made his first birdie on the par-3 16th. He has not gone a round this season without scoring a birdie.
“Michael and I were trying to set a goal after No. 7 to get two birdies to get back to even par on 18,” Spieth said, referring to his caddie, Michael Greller. “I gave myself those opportunities.”
Dustin Johnson, the winner of the United States Open, played in the afternoon and will have difficulty making the cut. His seven-over-par 77 was his worst round since January. It included two double bogeys and a bogey on 18, where he hit into a water hazard — one of only 16 bogeys on the easy par-5 finishing hole all day. Johnson declined to talk to members of the news media afterward.
Phil Mickelson, coming off a second-place finish to Stenson at the British Open, won this tournament the last time it was played at Baltusrol in 2005. But he hit only 7 of 14 fairways and 10 of 18 greens in regulation to open with a one-over-par 71.
“I just hit terrible shots for some reason,” Mickelson said. “I lost the rhythm and made some terrible swings. The game has been very easy, and then the first couple holes it became really hard.”