AUSTIN, Texas — Rory McIlroy put together another flawless back nine, running off five straight birdies.

This time, it wasn’t enough.

Former U.S. Amateur champion Peter Uihlein built a 5-up lead against McIlroy and held off his late charge with enough key shots of his own in a 2-and-1 victory, one of several surprises Wednesday in the opening session of the Dell Technologies Match Play.

Defending champion Dustin Johnson hit two shots out-of-bounds on the same hole, another tee shot in the hazard and couldn’t make the putts that he couldn’t afford to miss on the back nine. He wound up losing on the 17th hole to Bernd Wiesberger.

Justin Thomas also got a scare, mainly because his opponent had to putt with a sand wedge over the last 12 holes.

McIlroy was coming off a victory in the Arnold Palmer Invitational just three days ago, when he birdied five of his last six holes to win by three shots.

“I felt it was going to go two different ways,” Uihlein said. “When a guy comes off a win, next week out they’re either a little flat or still as hot as can be and they’re just going to blitz it.”

McIlroy was a little of both. He had a bogey, a double bogey and no birdies as Uihlein raced out to a 5-up lead through 10 holes. McIlroy began his run of five straight birdies on No. 12, and it might have been enough had Uihlein not matched him with a birdie at the 12th and another one on the 13th, when he laid up into the wind on the short par 4 over water and stuffed a wedge into 5 feet.

“I made him earn it at least,” McIlroy said. “I just came away a little fat. I didn’t really necessarily play badly. He didn’t make a bogey all day, so it was hard to sort of claw my way back.”

McIlroy, along with Johnson, Phil Mickelson and Tommy Fleetwood, now have to do some serious clawing to win their groups.