Novak Djokovic has crashed out of his own tournament at the hands of Aslan Karatsev, the Russian avenging his loss to the World No.1 in the Australian Open semi-finals.
Karatsev pulled off the biggest win of his career on Saturday as he shocked Djokovic 7-5 4-6 6-4 at the Serbia Open.
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It was the second shock exit on red clay in quick succession for Djokovic after he was beaten by Dan Evans in the third round of the Monte Carlo Masters last week.
The 18-time grand slam champion failed to convert a barrage of break points against Karatsev.
Djokovic, the 2009 and 2011 champion at the event which is played at a venue which carries his name, surrendered a 3-0 advantage in the opening set as he dropped serve three times.
The Serb then fell 4-2 behind in the second but summoned his well-documented powers of recovery to win four straight games and send the match to a deciding set.
Dubai champion Karatsev fended off eight break points in the third set before winning Djokovic's service game to move 4-3 ahead and leave the top seed on the brink.
Djokovic saved a match point down 5-3 to force Karatsev to serve it out. The third seed saved two further break points as he completed a landmark win after three hours and 25 minutes.
Karatsev to meet Berrettini in Serbia Open final
The Russian will meet Matteo Berrettini in Sunday's final after the Italian beat Japanese rival Taro Daniel 6-1 6-7(5) 6-0 in the other semi-final at Djokovic's tennis centre by the Danube river in Belgrade.
Djokovic praised Karatsev after what he said was a forgettable evening.
"Hats off to Karatsev, he was bold and deserved to win," Djokovic told an online news conference.
"I will probably not be able to recollect all the memorable rallies in this match because I lost.
"I am not happy with my performance, I put up a fight but he delivered great shots every time he needed to.
"I was unlucky at times, it all came down to one or two shots but I had too many ups and downs throughout the match."
Karatsev said: "This is definitely the most important victory of my career.
"At the Australian Open in Melbourne I felt like I was playing against a wall but this is a different surface and I was focused."
Nadal and Tsitsipas in Barcelona final
Meanwhile, Rafael Nadal and Stefanos Tsitsipas will do battle for the Barcelona Open title after both cruised into the final in straight sets.
Nadal beat fellow Spaniard Pablo Carreno Busta 6-3 6-2 on Saturday to stand on the brink of being crowned champion for a 12th time at the Real Club de Tenis Barcelona 1899.
Tsitsipas also maintained his magnificent run of form with a 6-3 6-3 defeat of rising star Jannik Sinner to set up a potential classic on Sunday.
"Tomorrow will be a very tough one. (Tsitsipas) is playing probably better than ever," Nadal said.
"Not one set lost in Monte Carlo and here, so it will be the toughest opponent possible. I hope to be ready."
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