Novak Djokovic is No. 1 in the ATP rankings for the 100th week.
The 26-year-old Serb is the ninth player to reach the milestone, joining Andre Agassi (101 weeks), Rafael Nadal (102), Bjorn Borg (109), John McEnroe (170), Jimmy Connors (268), Ivan Lendl (270), Pete Sampras (286) and Roger Federer (302).
Djokovic reached No. 1 in July 2011. He lost the top spot to Federer for three months in 2012 but regained it in November of that year.
Djokovic's bid to finish the year at No. 1 for a third straight time is under serious threat from Nadal. Djokovic has 11,120 points, while Nadal has 10,860.
Both are entered in next week's China Open, where Djokovic will be defending his title and Nadal has no points to defend. Nadal can get to No. 1 for the first time since July 3, 2011, by reaching the final.