Novak Djokovic advanced to the Vienna Open quarter-finals to essentially secure the year-end ATP No 1 ranking.
The Serbian, who beat Borna Coric 7-6 (13-11) 6-3 in Austria to reach the last eight, is currently at the summit having won all but two of his matches in 2020 - his controversial US Open default after hitting a line judge with the ball and defeat to Rafael Nadal in the French Open final.
He will face either Italian Lorenzo Sonego or Poland's Herbert Hurcakz for a place in the semi-finals.
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Djokovic knows the title in Vienna would seal the No 1 spot, while Nadal will only have the chance to surpass him if he takes up a wildcard for next month’s Sofia Open and Djokovic falls short this week.
Djokovic: It would be a dream to match Sampras' record
It is set to be a record-equalling sixth time Djokovic finishes as the ATP year-end No 1, matching Pete Sampras.
"Sampras had been one of my idols when I was a kid and of course I want to finish the year as No. 1 to tie his record," Djokovic told reporters.
"That's one of the toughest achievements in world sports."
Nadal, along with Roger Federer and Jimmy Connors, have finished as the year-end No 1 five times.
Novak Djokovic: I intend to play the Australian Open