McIlroy holed an eagle putt from just outside 10 feet on the par-5 16th at Caves Valley on his way to an eight-under 64, giving him a share of the lead with Jon Rahm and Sam Burns on Thursday.

Three days after heaving his 3-wood over the fence on his final hole at Liberty National, McIlroy used his new club – an old 3-wood he found in his garage – to smash a 285-yard shot up the hill and over a bunker that set up his eagle putt to move into a share of the lead.

McIlroy hasn't opened with a score this low since a 64 at the Tour Championship last year, and that's where he's trying to return. He is No.28 in the FedExCup, and only the top-30 after the BMW Championship make it to East Lake.

"I've went through playoff stretches before where you're always in that lead group. You're either 1, 2 or 3 in the FedExCup, and that can sort of take its mental toll," he said. "I'm in a position where I need to play well just to play next week. There is an element of free-wheeling."

Rahm and the man he is chasing on the FedEx Cup standings, Tony Finau, after round one. PHOTO: Tim Nwachukwu/Getty Images.

McIlroy has been feeling fatigued after going from The Open to a hot and humid Tokyo for the Olympics and then returning to the cooler climate of Memphis in early August. After a week off, he faced as many as three straight FedExCup playoff events.

"I was super tired yesterday. But you get a good night's sleep and you feel a little bit better the next day and you can go out and play well," McIlroy said.

As for Rahm, he is rested and relentless as ever.

The U.S. Open champion and World No.1 had five birdies on the front and kept bogeys off his card for a 64. It was the 15th time in his last 17 rounds dating to Sunday at the PGA Championship that he shot in the 60s.

Rahm is coming off a third-place finish in the FedExCup playoffs opener last week at Liberty National, losing a two-shot lead on the back nine. That might have bothered him more in the past, except that he was thrilled for Tony Finau, and he's become a fan of Ted Lasso.

The Spaniard as strong as a bull prefers to be a goldfish.

"Happiest animal in the world is a goldfish. You know why? He's got a 10-second memory," Rahm said, reciting a famous line from the Lasso series. "Played great golf last week, just a couple of bad swings down the stretch, and that's the most important thing to remember."

Burns also played bogey-free in posting his fourth score of 64 in his last eight rounds. A big week at Caves Valley might make him a popular topic for one of the six captain's picks for the Ryder Cup.

Eighteen players were at 67 or lower, a group that included Sergio Garcia (65), Patrick Cantlay (66) and Finau, Xander Schauffele and Dustin Johnson (67).

Finau won The Northern Trust last week after beating Cam Smith in a playoff.

The Australian is just a shot behind Finau after his bogey-free round to be joint 19th, one stroke ahead of compatriots Marc Leishman and Matt Jones (69), both of whom are tied 29th.

Leishman, a past winner of the BMW Championship, is looking for a top-10 finish to seal a spot in next week's 30-man season-ending Tour Championship in Atlanta.

- Doug Ferguson, Associated Press