DeChambeau has turned heads for years on the tour, openly seeking to perfect a style of play that leverages his size to generate better distance and club speed.
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The 27-year-old claimed his first major title with a six-shot victory at Winged Foot in New York, despite only hitting four of 21 fairways at one point in the tournament.
His unorthodox approach has long flummoxed golfing fanatics, and McIlroy was one of many to express surprise at the success DeChambeau had found at Winged Foot.
“I don't really know what to say because that's just the complete opposite of what you think a U.S. Open champion does. Look, he's found a way to do it,” McIlroy said.
“It's not the way I saw this golf course being played, or this tournament being played. It's kind of hard to really wrap my head around it.”
Despite DeChambeau’s vaunted advantage in hitting distance, the American pair only finished six and seventh in average total driving yards for the tournament - with McIlroy actually beating out his rival.
Nonetheless, the former world No.1 was still at something of a loss to explain DeChambeau’s victory.
“I think it's brilliant, but I think he's taken advantage of where the game is at the minute," McIlroy said.
“Look, again, whether that's good or bad, but it's just the way it is. With the way he approaches it, with the arm-lock putting, with everything, it's just where the game's at right now.
“I'm not saying that's right or wrong. He's just taking advantage of what we have right now.”
DeChambeau silences doubters with Open win
Bryson DeChambeau's unorthodox style received major validation as the power-driving "mad scientist" of the PGA Tour claimed the US Open with a commanding six-stroke victory that silenced the sceptics.
Since unveiling his single-length set of clubs at the start of his pro career, the former physics major has embarked on a one-man mission to revolutionise golf, facing plenty of doubts in a sport where tradition is valued above all else.
His most recent experiment was perhaps his most ambitious yet: a physical transformation that saw the 27-year-old pack on some 14kg of muscle with a high calorie diet and hours spent at the gym during the PGA Tour hiatus this year in order to add jaw-dropping velocity to his drive.
"I all of a sudden got a lot stronger, worked out every day, been working out every day, and all of a sudden - not because of clubs, but because of me - I was able to gain 20, 25 yards," DeChambeau said after bashing his way to glory around Winged Foot.
DeChambeau, who began the day two shots back of US Open debutant Matthew Wolff, mixed his prodigious length with clutch putts to shoot a virtually flawless three-under-par 67 and a six-under total.
"I did it. I did it. As difficult as this golf course was presented, I played it beautifully," he said after hoisting the trophy.
With Australian Associated Press/Amy Tennery