Novak Djokovic wrapped up his eighth year-end No. 1 ranking on Day 1 at the ATP Finals.

The Serb had to do it the hard was spending just over three hours to defeat Holger Rune 7-6(4), 6-7(1), 6-3.

“It means a lot,” Djokovic told the ATP. “You could see there were a lot of emotions on the court. I could feel it. I was very eager to win tonight’s match, get that monkey off my back. I won Paris, which put me in a much better position rankings-wise, and I knew coming into Turin I only needed to win one match. A big goal is achieved, everything else now is a bonus.”

In his ATP Finals debut, the 20-year-old Rune proved tough the opening set making waves on the Djokovic second serve, but the World No. 1 came out on top in a breaker.

Rune Was break early in the second however give it back, but Rune leveled in the breaker.

In the third and well after two hours of play, Rune was gassed and Djokovic pounced to claim his 19th straight match win.

“It took everything,” said Djokovic. “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… He was feeling the ball well, he was sharp. Very aggressive, every short ball he was coming in and he served terrific.”

Rune, who’s often been dubbed a Djokovic clone, falls to Djokovic for a second time in three weeks.

“We have had great matches always when we played,” Rune said. “Unfortunately I couldn’t do it today, but that’s how it is. I have to look forward and take the things out of the match I was happy with, take the things out of the match that I wasn’t happy with, and go back to the practise tomorrow and try to make them better.

Djokovic will next take on Jannik Sinner on Tuesday. The Italian opened up in excellent fashion in his opener cruising past Stefanos Tsitsipas 6-4, 6-4. Sinner had nine aces, never faced a break point and dropped just four points on first serve in the 85-minute win.

“I was excited to step on court and opening the Finals is really, really special,” Sinner said to the ATP. “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. I am happy to start off with a win and hopefully I can continue with this intensity.”

Tsitsipas shook off any issues with his elbow and back.

“He was attacking a lot, serving really well, kept his composure in those crucial moments that were a few today. He kept it quite clean and didn’t get too affected by any situation that came his way,” the former champion Tsitsipas said.

Tomorrow, Carlos Alcaraz makes his debut against former champion Alexander Zverev. The two have split all six meetings with Alcaraz winning both this year.

Russian best friends Daniil Medvedev and Andrey Rublev collide. Medvedev leads 6-2.