A stunning performance by world No.2 Carlos Alcaraz has earned the Spaniard a 6-4 6-4 victory over Russia's Daniil Medvedev to secure his place in the last four of the ATP Finals.
The 20-year-old erased any doubts about his form on Friday with a razor-sharp display in his final Red Group match to join Medvedev in the semi-finals of the year-ender.
Third seed Medvedev, who had already qualified, also produced some stunning tennis but Alcaraz pounced to snatch decisive service breaks in each set.
Despite his opening match loss to Germany's Alexander Zverev, Alcaraz tops the Red Group and will face Green Group runner-up Novak Djokovic in a mouth-watering semi-final.
"The most important thing that I did today is to stay strong mentally," said Alcaraz.
"There were a few games with my serve that I was struggling a little bit, his return game is amazing and he puts so much pressure on you. I think to stay calm, to stay strong mentally in those moments was the key."
The other semi-final will feature Medvedev against home favourite Jannik Sinner.
Group play concluded later on Friday when Alexander Zverev finished his season with a 6-4 6-4 win over Andrey Rublev, with neither player having a chance of advancing.
Rublev saved two match points before falling to a third-straight loss at the tournament without winning a set.
Zverev has had off-court issues recently after a German court issued a penalty order against him over allegations he caused bodily harm to a woman. Zverev has disputed the allegations and is contesting the penalty order.
Medvedev looked the more dangerous player in the early exchanges but failed to convert break points in the fourth game.
Alcaraz, who is making his debut at the tournament, then found another gear at 3-3 as he played four stupendous points to break to love.
He pounced again at 4-4 in the second set as some errors by Medvedev helped him secure the break of serve, before completing victory in emphatic fashion.
Alcaraz and world No.1 Djokovic will meet for the fourth time this season. The Spaniard lost to the Serb in the Cincinnati final last time out, although the youngster won their biggest meeting so far in an epic Wimbledon final, with Djokovic earning victory at the French Open.
"It's one of the most difficult challenges that I'm going to face, facing Novak in this tournament that he has won six times," said Alcaraz.
"Obviously Novak is Novak, he's the best player in the world right now. I'm going to put my best tennis out there and I'm going to enjoy it. I'm excited."