Spain's Carlos Alcaraz rebounded at the ATP Finals, securing victory over a struggling Andrey Rublev, while Daniil Medvedev clinched the first spot in the semi-finals with a win over Germany's Alexander Zverev.
Alcaraz eased to a 7-5, 6-2 win to revive his hopes in the Red Group after opening with a defeat by Zverev.
The 20-year-old will need to beat Medvedev in his final group game on Friday, although the Russian is guaranteed to progress from the group thanks to a 7-6(7), 6-4 win against Zverev, whose last group game is against Rublev.
Questions have been raised about the state of Alcaraz's game after a slump since winning Wimbledon.
But he responded to a three-match losing streak with a confident display, albeit against an unraveling Russian.
Rublev managed to hang on in the first set but wavered at 5-5 when he dropped his serve—Alcaraz then claimed the opening set with a comfortable hold.
Things deteriorated rapidly for Rublev when he dropped serve at the start of the second set.
He slammed down his racket after handing Alcaraz a breakpoint, and when he then blazed a shot wide, he repeatedly smashed his racket into his leg.
The Turin crowd gasped, and an emotional Rublev had to wipe blood off his knee during the changeover.
Alcaraz took complete control after that, with Rublev seemingly playing against the Spaniard and himself. The contest reached its predictable conclusion in a little more than an hour.
"It was a totally different match and level from mine. This is the level I have to play if I want to give myself a chance in this amazing tournament," Alcaraz said after his first win at the tournament, having missed out because of an injury in 2022.
"Yesterday was a good day for me in practice to find the level I needed to show today, and I think I did pretty well."
Zverev has won the title twice, in 2018 and 2021, but is in danger of missing out on a semi-final spot and will be kicking himself after some costly errors against Medvedev.
He led 4-1 in the opening set tiebreak and missed a volley. Then he had a set point but misfired a forehand into the bottom of the net to let Medvedev off the hook.
Medvedev, champion in London in 2020, then stole the opening set as Zverev failed with another high backhand volley.
World No. 7 Zverev had another chance at 4-4 in the second set but struck a wayward backhand to waste a breakpoint.
Medvedev then struck in the next game to break serve and win the match, taking his record against Zverev to 11 wins from their 18 meetings.