Top-seeded Serbian Novak Djokovic opened group play with a 7-6 (4), 6-7 (1), 6-3 victory over No. 8 seed Holger Rune of Denmark at the Nitto ATP Finals in Turin, Italy, on Sunday to clinch the year-end No. 1 spot in the ATP rankings.
Djokovic lands at No. 1 at year's end for the eighth time, an ATP record. At 36, he is also the oldest player to finish in the top spot.
"Becoming year-end No. 1 is an incredible accomplishment. To achieve it eight times is absolutely extraordinary," ATP chairman Andrea Gaudenzi said. "Novak continues to set the standard in tennis, and his passion and drive make him a true champion. There's no doubt that more greatness and records lie ahead in his journey."
With the victory, Djokovic improved to 1-0 in the Green Group.
The top eight players in the Pepperstone ATP Rankings were divided into two groups of four for the round-robin group stage. Italian Jannik Sinner, Greece's Stefanos Tsitsipas, Djokovic and Rune are in the Green Group, while Spain's Carlos Alcaraz, Alexander Zverev of Germany and Russians Daniil Medvedev and Andrey Rublev make up the Red Group.
The winners of each group will face the runners-up of the other group in the semifinals, with the third- and fourth-place finishers from each group getting eliminated.
Rune logged 18 aces and 48 winners on Sunday, but that still wasn't enough to get the best of Djokovic, who never trailed in the decisive third set.
"It took everything," Djokovic said. "I saw in the first game, when he fired shots from the baseline in the first three or four points, I knew that it was going to be a tough life for me. If I wanted to win this match, I was going to have to work really hard."
In Sunday's other match in the Green Group, fourth-seeded Sinner beat No. 6 Tsitsipas 6-4, 6-4.
Sinner won 32 of 36 first-service points and racked up 21 winners against five unforced errors to cruise to the win. Tsitsipas saved three of five break points and had 16 winners.
"I was excited to step on court and opening the Finals is really, really special," Sinner said. "I knew it was going to be very tough, but I think I handled the situation well. I tried to stay aggressive and I am very happy with the performance."
