After losing to Jiri Vesely in the quarterfinals of the Dubai Championships, Novak Djokovic will be replaced by Daniil Medvedev in the rankings.
The longest stay in the top spot for any man since the tour's computerized rankings began in 1973.
On Monday, he will become the 27th man to reach the top of the pyramid. He was the runner-up in the Australian Open the past two years.
Since Feb. 1, 2004, only one other man other than Novak Djokovic, Roger Federer, or Andy Murray has held the top spot.
It is great for tennis to have a new world No. 1 again, according to Jiri Vesely. A new generation is coming up. I think it's great.
It was the first tournament since he was deported from Australia for not being up to date with his vaccinations.
In the second round of the Mexican Open, Medvedev won.
If I do it it will mean a lot.
The Serbian player was beaten by the 123rd ranked Jiri Vesely in just under two hours to end his hopes of winning the title for a sixth time. They only faced each other once before, in Monte Carlo, where he won.
I never expected him to win again, said Vesely.
In the second set, Vesely served for the match at 4-5 but was broken by the Serbian.
The win was secured on his first match point.