Novak Djokovic did not become number one after being beaten by Jiri Vesely in the quarter-finals of the Dubai Tennis Championships
The Serbian is currently replaced by Daniil Medvedeb at the top of the rankings for the men's category.
Vesely said that he didn't think that he would actually stand a chance against noval, and it was a really great feeling.
Medvedev of Russia will become the first player besides Djokovic, Roger Federer, Rafael Nadal and Andy Murray to climb to the top of the rankings in 18 years.
Vesely beat the 20-time Grand Slam champion in 2016 on clay on Monte Carlo and repeated the feat on Dubai hardcourts.
Djokoavic's double fault on a breakpoint in the opening set gave Vesely the initiative to take charge of the match to serve
In the second set Djokovic fought back and equalized, but in the tie-break Djokovic slipped