Novak Djokovic will end the year as world number one for a record eighth time after he beat Holger Rune at the ATP Finals in Turin, Italy.
The 24-time Grand Slam champion overcame the Dane 7-6 (7-4) 6-7 (1-7) 6-3 in his opening Green Group match at the season-ending event on Sunday.
Victory for Djokovic extends his winning run to 19 consecutive matches.
The 36-year-old Serb won three Slams in 2023 to become the all-time record-holder of major titles.
Rune, 20, who is making his debut at the event, claimed the first break to lead 3-2 before Djokovic hit back and went on to win the opening set tie-break.
Rune reacted well and continued his streak of winning a set in every previous meeting with Djokovic to level the game in a second set tie-break.
Djokovic broke immediately in the deciding set, but Rune was able to respond before the Serb broke for a second time and ended the youngster’s challenge.
Djokovic is on course for a seventh ATP Finals title, which would make him the record-holder, having equalled Roger Federer on six last year.
