Andrey Rublev denied Novak Djokovic a first title of the season by beating the world number one in the final of his home tournament at the Serbia Open.
Faced with a partisan home crowd, world number eight Rublev dominated the deciding set to win 6-2 6-7 (4-7) 6-0.
Djokovic was visibly fatigued in the decider in what was a first final in a disrupted season for the Serb.
The win gives Russian Rublev, 24, a third title of the year and a first victory over Djokovic in his career.
Djokovic, 34, had only won two matches in 2022 going into the clay court event in Belgrade but showed his trademark grit to force a decider for the fourth match in a row.
However, Rublev crucially saved two break points in the opening game of the third set and from there dominated as his opponent struggled physically.
Djokovic's season started with his deportation from Australia in January which meant he missed the Australian Open.
He returned at the Dubai Tennis Championships in February but went out in the quarter-finals and then missed the US hard court swing, again because of his vaccination status. On his return to the tour, he suffered a shock defeat by Alejandro Davidovich Fokina in his opening match at the Monte Carlo Masters.
When 5-0 down in the decider against Rublev, Djokovic sat in his chair with his head in his towel as the home crowd loudly chanted his name.
But Rublev clinched the match with a forehand return winner - a shot Djokovic did not attempt to chase down - in the following game.