Davis Riley birdied three of his last four holes to seize the lead after Thursday's opening round of the PGA Memorial tournament, where last-hole setbacks deflated Rory McIlroy and Jordan Spieth.

Riley, ranked 79th, hasn't made a cut since taking his first PGA title in April with partner Nick Hardy at the tour pairs event in New Orleans.

But the 26-year-old American, a back-nine starter, sank a 13-foot birdie putt at the par-4 ninth to finish on five-under-par 67, one stroke ahead of England's Matt Wallace at Muirfield Village in Dublin, Ohio.

Riley credited a more relaxed approach for his round, blaming over-eagerness since his maiden PGA win for his string of missed cuts.

"I've been more and more eager to get there and have been in my own way a little bit," he said.

"I felt like I had a hard reset at the beginning of this week. I just tried to relax a little out there and hit every shot to the best of my ability. It was a good day and I had some good shots that kept momentum going."

Irishman Shane Lowry, the 2019 British Open champion, and England's Danny Willett, the 2016 Masters winner, were in a third-place pack on 69 that also included Canada's Adam Hadwin and Americans Spieth, Mark Hubbard, Austin Eckroat and David Lipsky.

Three-time major winner Spieth and playing partner McIlroy, a four-time major winner, were contenders when they reached the 18th hole, but Spieth made bogey and third-ranked McIlroy had a triple-bogey disaster.

McIlroy missed the green with his second shot from the right rough, found the rough again with his fourth before reaching the green and two-putting to salvage level-par 72.

Spieth holed out from a greenside bunker from 43 feet for birdie at the 10th, reached the green in two to set up birdies at the par-5 seventh and 11th and sank a 15-foot birdie putt at 17 before a closing bogey after finding fairway and greenside bunkers.

"It was one of those days where I got a couple out of the round, which was kind of nice," Spieth said.

Spieth has overcome the nagging left wrist injury that bothered him at last month's PGA Championship.

"I feel good. I wouldn't be playing if it was any bit of an issue at all," Spieth said.

"I just took enough time off."

Riley pitched his third shot inches from the hole to birdie the par-5 11th and added an eight-foot birdie putt at the fifth before his lone bogey at 18.

After a birdie from just inside four feet at the third, Riley caught fire late with birdie putts from just outside 12 feet at six, just inside five feet at seven and his closer.

"Those were holes that I kept momentum on and when I was on the green I felt like I had nice looks and I made putts," said Riley, who reached 11 of 18 fairways and 9-of-14 greens in regulation.

Masters winner Jon Rahm, the world number two from Spain, opened on 70 while top-ranked American Scheffler fired a 74.