Carlos Alcaraz leaned back, looked up and yelled in celebration.
He had just secured a spot in the semifinals of the ATP Finals in his tournament debut, setting up a match against top-ranked Novak Djokovic.
Alcaraz shouted "vamos, vamos," Spanish for "come on, come on," as he clenched his fists after beating Daniil Medvedev 6-4, 6-4 on Friday.
"It's one of the most difficult challenges that I'm going to face, facing Novak in the ATP Finals, where he has won six times," Alcaraz said. "Novak is Novak. He is the best player in the world right now. He's lost just six matches this year. He's unbelievable."
Alcaraz and Djokovic have played each other four times and won two each. Djokovic won their most recent encounter in the final in Cincinnati in August, while Alcaraz was victorious in the Wimbledon final.
"I'm going to play my best tennis and enjoy it the same way I did the past few matches," Alcaraz said. "I'm excited to face Novak."
Alcaraz, 20, is the youngest ATP Finals semifinalist since Rafael Nadal in 2006.
After missing last year's tournament because of an abdominal injury, Alcaraz got off to a shaky start at the season-ending event for the year's top eight players. He lost his opening match to two-time champion Alexander Zverev before getting back on track with a straight-sets win over Andrey Rublev.
That left him needing to beat Medvedev, who had already qualified for the semifinals, to advance. The Russian player didn't make it easy.
Medvedev had two break points in the fourth game, but Alcaraz came out on top of a 33-shot rally and then produced another big serve before going on to hold.
In the seventh game, Alcaraz broke Medvedev to love for the lead. He then held three set points but needed only one to take the opener with a powerful, crosscourt backhand.
After wasting two break points in the third game of the second set, Alcaraz got the decisive break when Medvedev double-faulted to allow him to serve for the match.
"This match was really, really tough ... but everything I did before this match I did almost perfectly so I'm really happy," Alcaraz said.
With Alcaraz advancing, the top four players in the world have qualified for the semifinals. Medvedev will face Jannik Sinner. Since the ATP formed in 1990, it's the fourth time the top four players all reached the semifinals at the ATP Finals, along with 1990, 2004 and 2020.
"At this moment he's in top form. The results prove it. He can do everything," Medvedev said. "I need to definitely be at my absolute best and better than today."
"You don't want to lose a match before playing semis. It's not the best feeling to lose a match. Your body reacts differently. Now I have to kind of regroup myself for tomorrow."
Zverev finished his season by beating Rublev 6-4, 6-4 in the late match, 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.
The Associated Press contributed to this report.