LOUISVILLE, Ky. — On a day in which he started slowly while everyone else seemed to burst out of the gate, Rory McIlroy kept his composure Sunday.
Fueled by a textbook eagle on the 10th hole, McIlroy shot a 32 on the back nine en route to a 3-under-par 68 and went on to win the PGA Championship at Valhalla. He finished at 16-under 268, one shot ahead of Phil Mickelson (5-under 66) and two ahead of Rickie Fowler (68) and Henrik Stenson (66). That trio shot a combined 1 under on their back nines.
‘‘Today wasn’t easy,’’ McIlroy said. ‘‘I didn’t get off to the best of starts. I needed to bide my time and wait for something to happen, and that something happened on the 10th hole. That eagle was a big turning point.’’
It was McIlroy’s fourth major championship, enabling him to join Jack Nicklaus and Tiger Woods as the only players to win four by the age of 25 since the Masters began.
‘‘Amazing. Incredible,’’ McIlroy said. ‘‘I’m not sure I’ll ever have another summer like this. I try and put this talk aside, but Tiger and Jack are two of the most successful players of all time. To be in their company at this age is very special.’’
The victory was another signal that McIlroy has a chance to be the most dominant player in golf since Woods was stacking up major championships.
‘‘Yeah, he’s good,’’ Mickelson said. ‘‘Really good.’’
McIlroy’s triumph came as darkness enveloped Valhalla, which was bracing for another rainstorm after being deluged at midday. A decision to let McIlroy’s group play in with Mickelson’s group ‘‘was no big deal,’’ Mickelson said, because it allowed everyone to finish.
It was the third victory in a row — including the second consecutive major — for McIlroy, who had won the British Open and the Bridgestone Invitational in his last two starts. He became the first player to win three consecutive starts since Woods won five in a row in 2007-08.
Symbolically, perhaps, youthful fan favorite McIlroy outlasted ageless fan favorite Mickelson, 44.
‘‘It was a fun day for me to get in the mix,’’ Mickelson said. ‘‘I’m disappointed in the outcome. Had I been able to finish those last five [or] six holes strong, it could have totally flipped the way I look at this year.’’
Taking aim at his sixth major title, Mickelson brought the biggest roars from the large gallery, which wasn’t deterred by a drenching rain that created rivers in fairways and ponds on greens and halted play for nearly two hours. With his first top-10 finish of the year, Mickelson made good on his goal to be an automatic qualifier for the Ryder Cup for the 10th time in a row. That’s a record on either side of the pond.
As he had done on his way to capturing his first three major titles, McIlroy led after three rounds before going on to win. He didn’t start off well, though. He bogeyed two of his first six holes and fell two shots behind Stenson and Fowler.
But starting with a terrific 3-wood that set up his eagle on the 586-yard 10th hole, McIlroy dialed up his ‘‘A’’ game. That meant accurate long drives, dead-on short irons and clutch putting.
On the back nine, McIlroy proved why he’s No. 1 in the world. While the others didn’t hold up down the stretch, McIlroy did. And that enabled him to hold up the PGA’s venerable Wanamaker Trophy.
‘‘This one probably hurts the most,’’ said Fowler, who finished tied for fifth in the Masters and tied for second at the U.S. Open and British Open. ‘‘The first three were a lot of fun. This one, I felt I could go out and win.’’