Carlos Berlocq recovered from failing to win a game in the opening set to stun top seed Tomas Berdych 0-6 7-5 6-1 and win the ATP Portugal Open.
The world no 62 from Argentina claimed the second title of his career and also his first ever victory over Berdych, who had accepted an invitation to play in Oeiras to continue his preparations for the French Open.
It seemed the Czech was coasting to glory when he breezed through the first set in 28 minutes, putting him on course to win his ninth tournament.
However Berlocq, whose other trophy came in Bastad last summer, put up a much sterner challenge in the second, eventually levelling matters when he broke in the 12th and final game.
He then raced into a 5-0 lead in the decider and although Berdych did manage to get a break back, it was only a case of delaying the inevitable. Berlocq duly clinched victory on his second match point when his rival netted a volley.
"This is truly a dream for me," said the South American. "To win this title today, I had to beat one of the best in the world. It was an honour to play and to win this final.
"It was really tough for me at the start, he was playing very aggressive. But I managed to slowly lift my game and get into the match.
"For me, the second set was like starting everything all over again. I managed to improve throughout the second and third sets and somehow I got the win."
Berdych admitted it was disappointing to suffer his sixth loss of the season, though he could draw positives on his work over the course of the week.
"This was a tough loss but Carlos played really well, he opened it up after the first set. He showed he's a big fighter and that he can do well on his court, on clay," said the 28-year-old.
"It was still a good week for me, I'm glad I could come and play as a wildcard.
"Everything went well up until the final. It's always disappointing to lose a match, but it's like that one day and different the next."