World number one Novak Djokovic beat Borna Coric to reach the Vienna Open quarter-finals and all but secure the year-end top ranking.
Australian Open champion Djokovic beat Croatia’s Coric 7-6 (13-11) 6-3 to reach the last eight in Bulgaria.
Djokovic has won five titles in 2020 including the Australian Open and lost just two matches – the French Open final to Nadal and a default at the US Open.
Djokovic could only be passed by Rafael Nadal, who would need to take a wildcard into next month’s Sofia event to try and overhaul him.
However, if he wins the title in Vienna on Sunday, he cannot be overtaken. He is now likely to draw level with Pete Sampras’ record of finishing as the year-end world number one