Little-known Kazakh Mikhail Kukushkin stunned top seed Mikhail Youzhny 6-3 7-6 in the St Petersburg Open final on Sunday to win his maiden title.
Kukushkin, playing in his first ATP final, broke the world number 10 twice to clinch the opening set.
The Russian served for the second set after breaking his opponent's serve in the 11th game but the 88th-ranked Kazakh broke right back to force a tie-breaker.
Youzhny had saved a match point to win his quarter-final on Friday, then four more in beating compatriot Dmitry Tursunov in Saturday's semi-finals, but he could not find a way past the 22-year-old from Astana.
Kukushkin dominated the tiebreaker 7-2 to seal victory after nearly 2-1/2 hours.
"What can I say, it was an amazing week for me," Russian-born Kukushkin, who moved to Kazakhstan two years ago, told reporters after pocketing the $113,600 -- by far the biggest prize of his career.
"Honestly, when the tournament started I didn't think I would last two rounds here, but I found myself playing in the final.
"Today I served well, played solid from the baseline, and also took my chances. That's the secret of my sucess."
Youzhny, who was aiming for his third title of the year, praised the winner.
"I don't want to look for excuses, the fact that I had to play two tough matches just to get to the final," the 28-year-old Muscovite, who won here in 2004, said.
"I would rather give credit to my opponent, who played really well today and fully deserved his victory."