Jaeger holds off top-ranked Scheffler for first PGA Tour title in Houston
Jaeger 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.
Playing partner Scheffler 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.
Jaeger, 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, Jaeger 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.
Jaeger 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.
Scheffler, who birdied the second and third before bogeys at the sixth and ninth saw him even for the day through nine, was right behind him for much of the day, until he missed the green at the 15th and fell two off the pace.
The US star clawed back a shot at the 16th, but couldn't get over the hump.
"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.
A good fight
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."
Scheffler wasn't the only player applying pressure on a crowded leaderboard.
Tosti emerged as the biggest threat, shaking off a birdie at the second with birdies at the third, eighth and 12th and grabbing a share of the lead on 12-under with a birdie at 16.
Along the way, he rattled in par-saving putts at the 13th and 15th, but after his chip at 18 left him an 18-foot par putt he couldn't get it to drop, closing with a 68.
Detry also posted a 68 while English journeyman David Skinns, playing in the final group with Scheffler and Jaeger, 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.