Novak Djokovic's bid for a record-breaking seventh ATP Finals title will continue after Jannik Sinner beat Holger Rune 6-2, 5-7, 6-4 and capped a perfect Thursday in which he became the first Italian to reach the semi-finals.
Sinner was already guaranteed a spot in the last four after Hubert Hurkacz claimed a set in his 7-6 (7/1), 4-6, 6-1 defeat to Djokovic earlier in the day, and the world number four topped the group after a battling win at the Pala Alpitour in Turin.
Sinner could have let Rune win as that would have eliminated Djokovic but the Italian's good friend Hurkacz, who played his only match of the season-ending tournament as a replacement for injured Stefanos Tsitsipas, poured cold water on that notion.
And Sinner fought hard to secure first place with his third win in three group matches and allow world number one Djokovic to follow him into the next round.
In the semis the reigning Toronto Masters champion will play whoever finishes second in the Red Group, while Djokovic will face the group winner.
Carlos Alcaraz and current Red Group leader Daniil Medvedev -- who is also already in the semis - face off on Friday afternoon before Alexander Zverev takes on eliminated Andrey Rublev.
Sinner initially looked like making short work of Rune despite the Dane only having to play three games in his previous match with Tsitsipas on Tuesday before the Greek dropped out of the tournament injured.
The 22-year-old came through a three-hour thriller against Djokovic but looked ready to take on the world when he broke Rune twice in the first three games.
Fatigue and a back niggle allowed Rune back into the match, but Sinner held firm to bask in the cheers of fans who chanted his name to the rafters.
Sinner's win saved Djokovic from a disappointing end to what has been an age-defying 2023 from the 36-year-old, who won three Grand Slams and took his 1000 Masters crowns to 40, another record.
Djokovic took control at the end of the first set of his match with Hurkacz when he rattled off nine points in a row to take a 6-0 lead in the tie-break and then seal the set.
However, he threw away his serve to love in game five of the second set and two games later looked on in disbelief as Hurkacz rammed home four consecutive aces from 15-40 down to go to within one game of drawing level.
Hurkacz easily saw out the set, drawing warm applause from the home crowd, and with the third set almost irrelevant the Pole collapsed against a visibly annoyed Djokovic, who hopes of a historic win are still alive.