Bernd Wiesberger upset World Number One Dustin Johnson to get his campaign off to a winning start at the WGC - Dell Technologies Match Play.
While Johnson was storming to an imperious victory last year, Wiesberger exited in the Group Stage but he won his fourth European Tour title at the Shenzhen International four weeks later and claimed a 3 and 1 win over the number one seed in Group 1 on his return to Austin Country Club.
Ian Poulter won the all-English battle against Tommy Fleetwood in Group 9, while there was also a win for Louis Oosthuizen in Group 8.
When Johnson won last season, he did not trail in any of his matches and when a Wiesberger bogey handed him the first, the four-time European Tour winner already had a mountain to climb.
A par was enough to put him all square on the third but he bogeyed the next before an out-of-sorts Johnson lost two balls in recording a quad on the sixth.
He gave me a couple of holes, I gave him a few. At the end of the day, I'm glad that I prevailed and got a win - Bernd Wiesberger
A Johnson bogey on the next meant he trailed at last but Wiesberger bogeyed the eighth before birdieing the ninth to lead at the turn.
When the American found water on the 11th, the shock was on, but when he birdied the 12th and Wiesberger was in the lake on the 13th, the duo were once again all square.
Johnson two-putted from seven feet on the 15th as Wiesberger edged back ahead and a birdie on the 16th had him two up with two to play.
"At the end of day, we both didn't have a great day," said Wiesberger. "He gave me a couple of holes, I gave him a few. At the end of the day, I'm glad that I prevailed and got a win.
"It wasn't his best day, it wasn't the best of my days. I think we both have to do a little bit of work this afternoon."
Adam Hadwin and Kevin Kisner halved their game in Group 1.
In Group 9, a poor chip on the first set the tone for Fleetwood and he dropped another shot on the second to quickly send Poulter two up.
The Race to Dubai champion birdied the sixth and a Poulter bogey on the eighth had him back level but when he found sand with his second on the ninth and failed to get up and down, Poulter led by one at the turn.
The lead was extended as the 42 year old took advantage of the par five 12th and Fleetwood found sand off the tee on the 15th for a bogey that left Poulter three up with three to play before he closed out a 3 and 2 win.
"Tommy is a great player," said Poulter. "I don't think either of us really holed any putts. I think I probably played just a little better than he did and obviously got it done.
"The simplicity of match play is win your match. It sounds really easy and it's not, so level of focus, level of concentration this week - be super aggressive, try not to hand too many holes away.
"I'm playing some of the best golf I've ever played, stats are proving that."
To get the first one in, sort of gives you momentum going into tomorrow - Louis Oosthuizen
In the other Group 9 game, Kevin Chappell beat Daniel Berger 3 and 2.
Oosthuizen had to survive an impressive fightback from Jason Dufner to win one up.
The duo were all square at the turn but Ooshuizen won the tenth, 11th and 12th before Dufner made a hat-trick of birdies from the 14th. A bogey at the 17th then halted the American's momentum and Oosthuizen sealed victory.
"It's tough when you lose the first one. You are sort of relying on the other guys for something to happen," he said. "I was in a similar spot last year where I actually lost my second round. To get the first one in, sort of gives you momentum going into tomorrow."
Jason Day - the two-time champion - was also a winner in Group 8, beating James Hahn 4 and 2.
In Group 16, England's Ross Fisher was two up after three holes against Japan's Yuta Ikeda but lost 2 and 1, while four closing birdies handed Zach Johnson a half with fellow American Matt Kuchar after being four down stood on the 15th tee.
