ORLANDO, FLA. -- The long ball helped Bryson DeChambeau outlast Lee Westwood on Sunday to win the Arnold Palmer Invitational, only the key shots were as much with his putter as his driver.

DeChambeau holed a 40-foot birdie putt on the front nine and a 50-foot par putt early on the back nine. He closed it out with a nervy 5-foot par putt for a 1-under 71 and a one-shot victory over the 47-year-old Westwood.

It matched the low score of the day, one of only three rounds under par in the toughest final round at Bay Hill in 41 years.

DeChambeau and Westwood were never separated by more than one shot over the final 15 holes, a fascinating duel of generations that came down to the last shot.

For the second straight day, DeChambeau revved up thousands of fans on the par-5 sixth hole by smashing driver over the lake and leaving himself 88 yards away on the 565-yard sixth hole. Westwood was 168 yards behind him, and raised both arms to jokingly mimic DeChambeau's reaction from the day before. They both made birdie.

DeChambeau appeared to be in trouble on the 11th when he narrowly missed going in the water off the tee, caught a plugged lie in the front bunker and gouged it out to 50 feet. He made that for par to stay ahead by one.

Westwood tied him with a 30-foot birdie putt on the par-5 12th, only to give it back with a three-putt on the 14th. The tournament turned on the par-5 16th, where it was Westwood who had the advantage.

DeChambeau's drive went up against the lip of a bunker and he had to lay up short of the water. Westwood had 158 yards and hit a poor short iron that came up short of the green. He chipped nicely, except that it rolled out 6 feet by the hole on the lightning-quick greens and he missed the birdie for a chance to tie.

They were tied going to the 18th when DeChambeau hit his most important drive of the day -- in the fairway. Westwood's tee shot settled in a divot, and he did well to get it on the green and two-putt from 65 feet. DeChambeau's birdie putt slid by some 5 feet and he shook his arms in celebration when the par putt dropped.

Westwood closed with a 73, not a bad score considering the average of 75.49 was the highest for a final round since 1980.

Corey Conners stayed in the mix until the very end. The Canadian holed a 15-foot eagle putt on the 16th to get within one shot, only to find a bunker on the par-3 17th and miss a 6-foot par putt. With a bogey on the final hole, he shot 74 to finish alone in third.

Jordan Spieth was part of a four-man race on the front nine and briefly tied for the lead with a birdie on the par-5 sixth. That turned out to be his last birdie of the day. He took bogey on three of his last four holes for a 75, dropping him into a three-way tie for fourth with Andrew Putnam (71) and Ricky Werenski (73).

For Spieth, it was his third top-five finish in his last four events.

DeChambeau said he received a text Sunday morning from Tiger Woods, who is recovering from serious leg injuries from his car crash in Los Angeles. He said Woods, an eight-time Bay Hill winner, told him to "keep fighting." He also considered the words from Arnold Palmer to "play boldly."

He needed all of that with the fight Westwood gave him, and the test Bay Hill provided.

"It's been quite a battle this whole entire time," DeChambeau said.

DeChambeau rose to No. 6 in the world with his ninth PGA Tour victory, and he became the first player this season with multiple victories, to go along with his U.S. Open title in September. It matched the longest it took for a multiple winner on the PGA Tour since 1969. Nick Price won his second title in the 21st week of the season in 1994.

Rory McIlroy, who started four shots out of the lead, was never in the mix. He came undone on the par-5 sixth, where he hit two tee shots into the water and then hit the fairway, green and made the putt to salvage double bogey. He shot 76.