Andrey Rublev produced a stirring fightback to defeat Stefanos Tsitsipas and reach the last four of the ATP Finals for the first time on Friday.
Rublev had failed to make it out of the group stage on each of his first two appearances at the season-ending showpiece.
It initially looked as if he would fall short once again in this winner-take-all clash with Tsitsipas, with both men looking to join Novak Djokovic in progressing from the Red Group.
He was outclassed by Tsitsipas in the first set but showed the grit to recover from 0-30 down in the opening game of the second to find a crucial hold of serve.
That proved the catalyst for a stunning turnaround, as Rublev dominated with his fierce forehand and a series of superb passing shots to seal a 3-6 6-3 6-2 victory in Turin.
He will face Casper Ruud on Saturday for a place in the final.
Rublev told Prime Video of that semi-final encounter: "I'm really looking forward because Casper is such a nice person, great player, great fighter, he has achieved so many things this season, so it's going to be a really good challenge for me."
Rublev – 10/2
Tsitsipas – 10/2
Rublev – 36/22
Tsitsipas – 25/12
BREAK POINTS WON
Rublev – 3/5
Tsitsipas – 1/3