The Frenchman arrived at Austin Country Club in fine form, with his second win in six events at the Commercial Bank Qatar Masters earning him a place in the field.
Despite that, he was still seen by most as an underdog against World Number Five DeChambeau, who arrived in Texas off the back of a victory at the Arnold Palmer Invitational presented by Mastercard and a third-place finish at the Players Championship in his last two events on the US PGA Tour.
But after going ahead for the second time on the fourth, he never looked back, keeping his nose in front and surviving a late DeChambeau fightback to seal victory with a birdie on the last and take the early lead in Group Five.
"I think in match play everyone is on the same level, so no, I don't think it's an upset," he said.
"Obviously he's a heck of a player. He hit the ball so far. I think it's just a round of golf. It doesn't matter who you are. In one round you can beat anyone.
"Being able to beat the World Number Five, it's not every day that I can play match play against the World Number Five in a tournament. I just enjoyed it.
"I was just trying to put a solid round of golf (together) and I think I did that pretty well, especially on the front. I didn't make any mistakes really on the front and being three up after 12 holes I think was a good enough lead.
"I was actually feeling a little bit nervous at some point on the back nine but I think being three up was good enough and I'm just very happy I won that match."
Rozner converted from 12 feet for a birdie at the second to go one up and although he hit his second to within 20 feet at the second, it was DeChambeau who made the birdie to get back to all square.
Rozner responded immediately with another great iron shot and another birdie from 12 feet at the par three fourth and was two up at the turn after holing from similar distance at the ninth.
The lead was briefly three as Rozner made the most of the par five 12th but he had to concede the 13th and when he found water off the tee at the 16th and DeChambeau recovered in excellent fashion after a poor tee shot of his own, the gap was just one.
It was advantage DeChambeau off the tee at the last but Rozner played a remarkable flop shot to seven feet from the rough and sealed victory.
Kim was two up after two holes, maintained that lead at the turn and took a one up lead down the last.
But the 2017 Race to Dubai champion made a clutch ten footer to birdie the 18th and snatch a half.
The Australian won the fifth, seventh and 11th but was instantly pegged back on all three occasions.
Perez then hit the front as he put an approach to five feet on the 13th and hit a stunning driver off the deck to hit the 16th green in two and go two up with two to play.
"To me, match play is just like playing on Sunday," he said. "It's pretty much right in front of you. You know what to do, which gives you clarity. You don't have to think, 'oh, maybe the guy in front is making a run or the guy behind' - it's right there in front of you."
The Scot was one down after 12 in a tight affair but chipped in for eagle after driving to the side of the 13th and Na bogeyed the next before MacIntyre holed a bunker shot for another eagle on the 16th.
In Group Seven, debutant Christiaan Bezuidenhout holed a 17 footer on the last in a birdie-birdie finish to halve his contest with Joaquin Niemann, while Patrick Reed also won his last two holes to salvage half a point against 2018 champion Bubba Watson.