JACKSON – Peter Malnati finished his final round with a one-stroke lead. He then went to the clubhouse, where he watched the rest of the tournament on TV, talked with his wife and even did a few pull-ups to stay loose.

Turns out the extra exercise wasn’t needed. He had his first PGA Tour victory already wrapped up.

The 28-year-old Malnati shot a 5-under 67 on Monday to rally past a crowded leaderboard and win the Sanderson Farms Championship, beating William McGirt and David Toms by one stroke.

Malnati finished at 18 under in a rain-soaked tournament that was forced to complete play Monday. He was one shot behind going into the final round but closed with five birdies over his last 12 holes.

He was remarkably calm down the stretch, avoiding trouble at the Country Club of Jackson. He made par on his final three holes, sinking a 3-foot putt on No. 18 to hold his one-stroke lead.

Then, it was time to wait.

“It was kind of all surreal at that point,” Marnati said. “I was definitely happy. I don’t really know what all I was feeling.”

Soon enough, he was feeling like a PGA Tour winner. The victory continued a trend for younger winners: He’s the fifth first-time winner in five events this season.

The waterlogged event in Jackson was delayed five times, either by rain, lightning or darkness. The final day was a long one for several players, with some finishing as many as 30 holes.

The leaderboard was constantly changing throughout Monday’s marathon round, with about 15 players moving in and out of contention.

Roberto Castro led through the first two rounds but shot a 3-over 75 in the third round. He finished at 16 under in a tie for fourth.

Malnati was one of the few constants throughout the day. He had back-to-back bogeys on Nos. 5 and 6, but quickly recovered with birdies on four of the next six holes.

Malnati said he promised himself he wouldn’t be watching the scoreboard if he was in contention during the final round, but curiosity overwhelmed him when he was on the 18th green.

He turned to his caddie Shane Joel and asked how he was doing in relation to the field.

Joel’s response: “How about we just hit a good putt right here.”

He did. It earned him a $738,000 paycheck and an exemption for the next two-plus years.

“I’m not a big stats guy, but I’ll enjoy looking at my stats because I bet I hit a lot of greens, particularly over the last two rounds,” Malnati said.

This is Malnati’s second go-round on the PGA Tour. He struggled as a rookie in 2014 and lost his card, but re-gained it after finishing ninth on the Web.com Tour last season.

Patton Kizzire and the 48-year-old Toms had a one shot lead after the third round before shuffling back into the pack early in the final round.

Toms still hung around the leaders all day, but couldn’t quite make the charge for his 14th career win. He had four birdies on the back nine.

By DAVID BRANDT, AP Sports Writer