Daniil Medvedev will officially take Novak Djokovic's World No.1 ranking next week after the Serb suffered a shock loss to Jiri Vesely in Dubai on Thursday.
Playing his first tournament of the year following his deportation from Australia, Djokovic had looked in impressive form in his first two matches.
But it all came undone in the quarter-finals as the 20-time major winner went down 6-4 7-6 (4) to the World No.123.
A combination of some unusual mistakes and an inspired southpaw opponent contributed to the defeat that spells the end of Djokovic's current two-year reign at the top of the rankings.
The Serbian has sat at World No.1 since overtaking Rafael Nadal on February 2, 2020 - setting a new record last March for most weeks at the top that currently stands at 361.
But next week that position will be taken by US Open champion Medvedev, who is through to the quarter-finals of the Mexican Open in Acapulco.
The Russian knew going into this week that a title would guarantee him top spot, and speaking at the weekend, Djokovic said: "He deserves to be No.1.
"Eventually it's going to happen. If it happens this week, I'll be the first one to congratulate him."
Medvedev, who suffered a five-set loss to Nadal in the final of the Australian Open last month, will become the first man other than Djokovic, Nadal, Roger Federer or Andy Murray to hold the World No.1 ranking since Andy Roddick in February of 2004.
Vesely is currently ranked No.123 but has been playing well above that this week, and the 28-year-old is the lowest-ranked player to beat Djokovic for almost four years.
Djokovic retrieved an early break but Vesely, who won their only previous meeting in Monte Carlo six years ago, pressured the top seed's serve again in the seventh game and held his nerve to take the first set.
He broke Djokovic for a third time in the seventh game of the second set, and although he was unable to serve out the victory, Vesely claimed the tiebreak to secure a famous win.
Tennis fans and commentators were left in disbelief.
Vesely's run in Dubai has been insane! Routs Cilic, Bautista Agut and Djokovic. Next stop SF. https://t.co/AD57ZOFb7z
— Three.Eyed.MD (@ThreeEyedMD) February 24, 2022
Only 4 men’s tennis players have held the world #1 ranking in 18 years. Unbelievable stretch of dominance from primarily Federer/Nadal/Djokovic. https://t.co/dDjBbt1WNa
— Seth Wisner (@SethWisner) February 24, 2022
Djokovic will be disappointed by his loss today but also he will tip his hat to the unbelievable performance from Vesely!!
Novak played 2 great matches at a very high level & will use that going forward. Was incredible to see the support he got & he'll get that most places!!
— Reggie🐺🐊 (@Reggie61823972) February 24, 2022
Holy crap. I didn’t even check the #DDFTennis scores bc I really figured that with that draw Novak Djokovic would coast. But with that loss, Daniil Medvedev will become the new world #1, the first outside the Big 4 since Andy Roddick!!!! https://t.co/s0F16E9jnk
— Sarah (@Sarah_Oestreich) February 24, 2022
Oh. My. God. Vesely literally 2-0d Djokovic ex #1 😱😱
— NEO (@NeoBetting) February 24, 2022
Wow, first time in 18 years a member of the big 4 isn’t going to be #1, this day was gonna happen eventually. I can’t believe it’s really been that long. Speaks volumes to how good Nadal, Djokovic, Federer and Murray have been for so long. I don’t think we’ll be seeing this again
— Eric (@Emoney_312) February 24, 2022
for the first time since i’ve started watching tennis, i’ll know a world number 1 not named federer, nadal, djokovic or murray. i genuinely can’t believe it
— ∞ (@fakkythecreator) February 24, 2022
Novak Djokovic set to lose World No.1 ranking
Djokovic told reporters after the match: "Unfortunately, it wasn't my day."
"I congratulate Jiri. He played better. He just went for his shots.
"His serve was big. His whole game was big.
"I expected myself to play on a higher level, for sure. I mean, I can do better. But credit to Jiri."
Vesely said: "It's an amazing feeling. I never really thought I would have a chance against Novak.
"He is one of the greatest of all time.
"It is great for tennis to have someone new at World No.1.
"Novak is such a champion, he has been number one for 361 weeks, but tennis needs new World No.1s and there is a new generation coming up."
Djokovic admitted he struggled to find his rhythm.
"The more matches I play, the more confident I will be, the more comfortable I'll be feeling on the court," the 34-year-old said.
In the semi-finals, Vesely will play Canadian Denis Shapovalov, who defeated Ricardas Berankis 7-6 (7-4) 6-3.
The other last-four match will feature Andrey Rublev, who came from a set down to beat American Mackenzie McDonald 2-6 6-3 6-1 against Hubert Hurkacz, who earned a notable 6-3 6-3 triumph over rising Italian Jannik Sinner.
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