Stephan Jager holds off top-ranked Scheffler for first PGA title in Houston
Jager took the solo lead at 12-under with his fourth birdie of the day at the ninth, then parred all nine holes on the back nine to emerge with the victory on 12-under 268.
"It feels amazing," Jager said. "I couldn't have dreamed up a better week to do it.
"Obviously playing Scottie last couple days, he's been on a tear, so to kind of slay the dragon a little bit this week was amazing.
"He's such a good dude, such a good player, I was just happy to play with him a couple days."
Scheffler, playing in the last group with Jager, responded to a bogey at the demanding par-three 15th with a birdie at 16, but he missed a five-and-a-half-foot birdie putt at 18 that would have forced a playoff.
He settled for a two-under par 68 that put him in a five-way tie for second alongside Taylor Moore, Tony Finau, Belgian Thomas Detry and Argentina's Alejandro Tosti.
Tosti was 12-under after a birdie at 16, but closed with a bogey at 18.
Jager, ranked 71st in the world and chasing a first tour title in his 135th start, was part of a five-way tie for the lead to start the day.
After a five-foot birdie at the third, he rolled in a 23-foot birdie putt from the fringe at the fourth to maintain a share of the lead.
After a bogey at the seventh, Jager made a three-foot birdie at the eighth and rolled in an eight-foot birdie at the ninth to make the turn with the solo lead.
Jager barely missed a 20-foot birdie at the 12th, then drilled a 19-foot par-saving putt at the 13th. He parred 16 after his drive went left onto a cart path.
Jager said patience was "the name of the game" on the potentially treacherous back nine, so he was pleased to avoid bogeys.
"I really didn't hit many bad shots," he said. "I didn't feel like I was playing defense at all. It's just this game is very hard."
Scheffler, who birdied the second and third before bogeys at the sixth and ninth, was just behind Jager until he missed the green at 15 and fell two adrift.
The US star clawed back a shot at the 16th, but couldn't get over the hump - even though Jager was "100%" expecting a playoff when he saw how close Scheffler was for birdie at the last.
A good fight
"I put up a good fight," said Scheffler, who ended a near year-long title drought with a win at Bay Hill then won the Players Championship.
He was trying to become the first player since Dustin Johnson in 2017 to win three consecutive tour starts.
"Felt like I had some weird breaks this week," Scheffler added. "It's tough to describe, but obviously I'm a bit disappointed.
"I hit two or three really good shots into 18 to give myself a chance and I feel like I made the putt and I looked up and it was breaking off.
"So a bit disappointing, but Stephan played great this week and he's a deserving champion."
Scheffler said he wouldn't dwell on his last missed putt.
"It would be one thing if I pulled it or something like that," he said. "I just misread it. I don't know why I misread it, it's part of the game."
Tosti emerged as a late threat, shaking off a bogey at the second with birdies at the third, eighth and 12th and grabbing a share of the lead with a birdie at 16. But he couldn't sink an 18-foot par putt at 18 and closed with a 68.
Detry also posted a 68 while English journeyman David Skinns, playing in the final group with Scheffler and Jager, was two-under for the day and 11-under for the tournament through 16 but bogeyed the last for a 69 and a share of seventh on 270.