Turin, Italy — Novak Djokovic has secured the year-end No. 1 ranking for a record-extending eighth time.

Djokovic needed only one match win at the ATP Finals to be sure of keeping the top spot and the 24-time Grand Slam champion did it in his opener, beating Holger Rune 7-6 (4), 6-7 (1), 6-3 over more than three hours on Sunday and into Monday morning.

"It was a very emotional and tough win because of the significance of tonight's match," Djokovic said. "That was added pressure, and attention."

"It means a lot," Djokovic added. "You could see there was a lot of emotions on the court. I could feel it. I was very eager to win tonight's match and get that monkey off my back."

The 36-year-old Djokovic had already moved ahead of previous record holder Pete Sampras (six years at No. 1) two years ago.

Carlos Alcaraz took the honors last year.

After this tournament, Djokovic will become the first player to hold No. 1 for 400 weeks, with Roger Federer at 310 the only other man to eclipse the 300-week mark.

If Djokovic raises the trophy next weekend, he'll break a tie with Federer and capture a record seventh title at the finals.

"A big goal is achieved; everything else now is a bonus," Djokovic said.

Djokovic has won 19 straight matches stretching back to his five-set loss to Alcaraz in the Wimbledon final in July.

Earlier in the same group, Jannik Sinner beat Stefanos Tsitsipas 6-4, 6-4.

Djokovic ended a close first set with a blazing forehand return winner — then flexed his right biceps and held the pose for a few moments before unleashing an authoritative fist pump.

The 20-year-old Rune was making his debut at the season-ending tournament for the year's top eight players and pushed Djokovic to a deciding set for a fourth straight time in five career meetings.

Djokovic also beat Rune in three tight sets at the Paris Masters this month.

After Djokovic gave up an early break in the third, he broke two rackets with his foot before sitting down for the changeover. But he quickly regained his composure — and the lead — before finishing the match off shortly after midnight.

SINNER'S SERENADE

"Olé, Olé, Olé Olé, Sin-ner, Sin-ner."

The way the crowd serenaded Sinner after his brisk win over Tsitsipas in the opening match of the tournament made it sound like a soccer stadium inside the Turin arena.

Before the Italian could respond during an on-court interview, fans started singing his name so loudly that all he could do was step back, smile and say, "Grazie."

"The feeling is this," Sinner said. "Kind of a football stadium. Also with the roof closed, it's a little bit louder. It's nice. It means that the people, they really care about me."

Under an enormous spotlight as the poster boy for the tournament, Sinner didn't show any nerves at the season-ending event for the year's top eight players.

Supported by chants of "Vai Jannik" ("Go Jannik") and signs that read "Facci Sognare" ("Let us dream"), Sinner gave the fans just what they came for with his blistering baseline shots and strong serve.

The 22-year-old Sinner is finishing up a year in which he has claimed four titles including his first Masters 1000 trophy and is up to a career-high No. 4 in the rankings — the first Italian that high since Adriano Panatta nearly a half-century ago.

Sinner even showed off some of his newfound touch when he produced a backhand topspin lob winner while on the run early in the second set.

Then on his first match point, Sinner spun an ace out wide on the deuce court to finish the match off in 1 hour, 25 minutes.

It was Sinner's tour-leading 14th win indoors this year — against just one loss.

"The match went really, really well and the crowd support was crazy," Sinner said. "It's not just about improvement, it's about destinations and the destination I wanted to reach this year was to be here."

Sinner served nine aces to Tsitsipas' six amid fast conditions inside the Pala Alpitour and didn't face a single break point.

"He definitely has improved his serve, and he showed it today," Tsitsipas said. "There wasn't much I could do. I was trying to guess sometimes. He serves really close to the lines, to the corners. ... I'm not the Elastigirl from the superheroes to be behind these balls."

Tsitsipas, the 2019 champion, had cut short a practice session on Friday due to an apparent physical issue but he said he was "absolutely fine."

Matches in the other group on Monday feature Carlos Alcaraz vs. Alexander Zverev and Daniil Medvedev vs. Andrey Rublev.

The top two finishers in each group advance to the semifinals.