Stefanos Tsitsipas of Greece, the youngest player in the top eight at ATP World Tour Finals, clinched his first win here on Monday, beating World No. 4 Daniil Medvedev from Russia 7-6(5), 6-4 in their sixth meeting.

The two debutants of the season finale unveiled the match for Group Andre Agassi with Medvedev leading the head-to-head in 5-0.

Tsitsipas, 21, said defeating Medvedev to win his first match in the Finals meant more than extra.

“It’s a victory that I craved for a long time and it’s great that I came in at this moment.”

Last month, the 23-year-old Medvedev beat Tsitsipas 7-6(5), 7-5 in Shanghai Masters semifinal and went on to claim the title.

“I think just general energy was not the way I wanted. And talking about energy, I’m not talking only about physical. Mentally I was missing something. I didn’t have good energy enough to get the win today,” said Medvedev.

Tsitsipas said, “I knew that I was in good shape and in good form. I learned from my previous mistakes in Shanghai. I remember coming out of my match in Shanghai against him and saying to my coach that things are going to be different next time.”

sitsipas improved to 1-5 against Medvedev in their ATP Head-2-Head rivalry. The Russian defeated Tsitsipas twice this year at Masters 1000 in Monte-Carlo and Shanghai.

”It’s one of the most important victories in my career so far. I gave myself a big boost today, kept believing, kept fighting. It’s such a relief,” Tsitsipas said. “It’s not easy coming in knowing you’ve lost five times before, but I made a deal with myself that I’ll keep trying until I get it. It doesn’t matter if it’s 10, 20 times.

”This victory means a lot to me and this crowd means a lot to me. So much love, so much support, Greek flags everywhere. It almost feels like I’m playing in Athens.”