World No 1 Novak Djokovic kept alive his hopes of winning a record seventh ATP Finals title after beating Hubert Hurkacz 7-6, 4-6, 6-1 in Turin.
Djokovic needed the victory to remain in contention for the semi-finals after losing to Jannik Sinner in a marathon match last time out, but is still reliant on the Italian beating Holger Rune later on Thursday.
World No 4 Sinner is guaranteed at least second spot in the Green Group thanks to Hurkacz, who played his only match of the season-ending tournament as a replacement for the injured Stefanos Tsitsipas, securing the second set against Djokovic.
He becomes the first Italian in the competition's 54-year history to reach the last four and can afford to lose against Rune, which would put Djokovic out of contention in the process.
That would be 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, which was another record.
“My kids are arriving tonight, so I don’t think I’ll watch,” said Djokovic, who would surpass Roger Federer to stand alone with seven ATP Finals titles. “I did my job and I’m going to spend tonight with the family. Then tomorrow I can worry about whether I qualified or not.”
All three of the Serbian's group-stage matches have gone to three sets, meaning the defending champion has spent more than eight hours on court at Pala Alpitour.
Playing with nothing to lose, Poland's Hurkacz was a force to reckon with on serve – firing 24 aces in the match – but he ran out of steam in the final set as Djokovic converted break points for the first time in the contest.
He took control at the end of the first set when he rattled off nine points in a row to take a 6-0 lead in the tiebreak 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 to a visibly annoyed Djokovic.
The 24-time Grand Slam champion now holds a 7-0 head-to-head record against Hurkacz as targets a 12th semi-final berth in 16 appearances at the Finals.