Shane Lowry lost a three-shot lead with two double-bogeys on the 16th and 17th to hand Nico Echavarria the title in the final round of the Cognizant Classic in Florida.
Lowry, the joint-overnight leader following a bogey-free 63 on Saturday, was in a commanding position after making four birdies and an eagle at the 10th over the first 13 holes.
But the Irishman was undone by consecutive double-bogeys at the par-four 16th and par-three 17th, both resulting from tee shots that drifted way right and into the water.
That swiftly ended Lowry's title hopes and meant he had to settle for a three-way share of second.
"I'm obviously extremely disappointed. I had the tournament in my hands, and I threw it away," Lowry said.
"What more can I say? That's twice this year now so far. I'm getting good at it.
"I played unbelievable all day, and one bad shot on 16 completely threw me for the last three holes. It's never happened to me before.
"I said to [my caddie] Darren (Reynolds), how do I feel like this now when I went through what I did last September in Bethpage and got through that fine.
"But I beat myself today. I hit two really bad shots at the wrong time, and that's what this course does to you."
Echavarria, on the other hand, claimed his third career PGA Tour title with a 66, putting him at 17 under thanks to an impressive bogey-free weekend for the Colombian.
"It was a blessing today," Echavarria said.
"I didn't have my best off the tee, but I was able to manage.
"I had some good breaks. To win out here, sometimes you have to have good breaks - if you're not Scottie Scheffler that hits it every time in the perfect place! So I'm happy with how it went."
Lowry shared second place on 15 under with American duo Austin Smotherman - the other joint-overnight leader - and Taylor Moore.
Brooks Koepka also roared back up the standings with a course-best 65 as he continues to find his form after his recent return to the PGA Tour from LIV Golf.
"Yeah, I played really solid the last three days," Koepka said.
"Didn't quite hit it that great yesterday, but just controlling shots I think a lot better.
"Putter obviously has gotten better. I haven't looked at the stats, but just that little adjustment Thursday night made a huge difference.
"Finally found some confidence. I think that's the one thing that's been lacking."
Jordan Smith and Aaron Rai ended up as the highest-placed Englishmen, after Smith's impressive final-round 68 tied him with Rai at 23rd on the leaderboard.
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