An astonishing collapse ended Novak Djokovic’s bid for an unprecedented men’s “golden slam” as Germany’s Alexander Zverev reached the 2020 Olympic Games final 1-6 6-3 6-1 in Tokyo on Friday.

The world number one Serbian looked in complete control as he took the opening set with ease.

He broke for 3-2 in the fifth game of the second set to move to the verge of victory.

But Zverev immediately broke back to spark an eight-game winning run which leveled the match and put him in a commanding 4-0 lead in the decider.

Djokovic recovered to offer some resistance but could not repair the damage as Zverev claimed 10 of the last 11 games to win.

Zverev was congratulated by Djokovic at the net but then took time to compose himself beneath his towel at the empty  Ariake Tennis Park.

The 24-year-old Zverev, fifth in the world, will now take on the 25th-ranked Russian Karen Khachanov for the biggest title of his career in Sunday’s final.

Neither of the two has won a slam, though Zverev did lose the 2020 US Open decider.

The defeat ends Djokovic’s attempt to become the first man to win all four grand slams plus Olympic gold in a season.

It was only Steffi Graf who  in 1988,  achieved the feat on the women’s side.

The Serbian can still become the only third man to claim a calendar year grand slam if he wins the US Open which starts in a month’s time.

American Donald Budge, in 1938, and Australia’s Rod Laver have only achieved this feat, in 1962 and 1969.

Meanwhile, in the other semi-final game at the Tokyo Games, Khachanov defeated Spain’s Pablo Carreno-Busta 6-3 6-3 to reach the final.

Djokovic and Carreno-Busta will contest the bronze medal match on Saturday.

Djokovic will return to partner Nina Stojanovic in the mixed doubles semi-finals, hoping to set up a final meeting with Australians Ash Barty and John Peers