Brennan came into the final tournament of the regular season at No.105 in the FedEx Cup, a disappointing year with only one top-10 finish. Now his season gets extended by at least one week after his second PGA Tour title in two years.
Brennan was one shot behind Hossler when he ran off five straight birdies starting on the fourth hole. That turned a deficit into a three-shot lead at the turn when Hossler took a bogey on the ninth.
Then it was a matter of hanging on for 24-year-old Brennan.
"I don't want to be done playing golf," Brennan said. "Unfortunately, I've had a couple of tough Sundays. Outside of that, I had been playing really solid. This is my sixth week in a row. I'm perfectly happy running on fumes next week."
The FedEx Cup playoffs start on Thursday with the St Jude Championship in Memphis, Tennessee. Only the top 70 players advance, and Brennan shot up to No.47.
Jackson Koivun, who left Auburn in June and won the 3M Open in only his third PGA start, narrowly hung on to the 70th spot and goes from college to the post-season in only two months.
But he had to sweat it out after closing with a 71. Matt Wallace and Davis Thompson were still on the course and in range of finishing high enough to bump Koivun out of the top 70, but they failed to hole key putts, and Koivun made it with eight points to spare.
A bogey might have been enough to knock him out of the post-season. But on the 18th hole at Sedgefield Country Club on Sunday, Koivun piped his drive straight down the middle, leaving a wedge from the fairway and an easy par.
Brennan started feeling the nerves, too. He was four shots behind in a tie for fourth going into the final round of the 3M Open and shot 74 to finish out of the top 20. Last week at the Rocket Classic, he was in the final group and one shot out of the lead, but closed with a 73 to tie for 15th.
He delivered in the final event of the regular season, and it was his mother who came on to the 18th green to celebrate who reminded Brennan the victory also sends him to the Masters. He made his Masters debut this year, going from the PGA Tour Americas straight to the big leagues after he won the Bank of Utah Championship.
Brennan made birdie on the final hole to finish at 22-under 258, matching the tournament record at Sedgefield. He finished three shots clear of Hossler, who carded a final-round 67.
Ben James, the No. 1 player from the PGA Tour University ranking who has a card already secure for 2027, fell out of contention on Saturday but roared back with a 61 to finish third.
Brennan was the only player to move into the top 70, replacing Steven Fisk, who was No.69 but missed the cut at the Wyndham Champion and fell to No.71.
Also failing to advance to the post-season was Brooks Koepka, the first player to rejoin the PGA Tour after being at LIV Golf. Koepka needed a fourth-place finish but could only manage a tie for 67th.
