"I want to step it up and show better tennis next time" - Stefanos Tsitsipas after losing his ATP Finals opener to Andrey Rublev

Stefanos Tsitsipas started his 2021 ATP Finals on a disappointing note, losing 6-4 6-4 to Andrey Rublev. The Greek never really found his footing in the match which, coupled with Rublev's strong showing, led to a lopsided defeat.

At his post-match conference, Stefanos Tsitsipas admitted that his performance could've been better. He also complimented Andrey Rublev's play and sounded especially impressed by his serve, stating that it was perhaps one of his best ever serving displays.

"Could have been better," Tsitsipas said. "I thought Andrey played really well. He was serving at his best that I have ever seen him serve. I think in the first set he had, I don't know, something like 22 consecutive first serves. Maybe the stats are different, but that's the feeling I have. It was pretty good on that side."

Tsitsipas had earlier mentioned feeling some pain while practicing. But when asked if that played a role in his loss on Monday, the 23-year-old declined to elaborate.

"I prefer not to comment on that," he said. "Thank you."

Tsitsipas went on to claim that he's still excited for his upcoming matches. The Greek has a chance to progress to the semis despite losing his first match, and he wants to make the most of it by playing better next time.

"Well, I'm excited," he said. "I mean, I still, you know, want to play good tennis, and despite the loss today I'm given more chances. I want to step it up and show better tennis next time."

Stefanos Tsitsipas's excitement at playing in the ATP Finals hasn't faded over time

Stefanos Tsitsipas with Novak Djokovic at the 2021 ATP Tour Finals promo shoot.

Stefanos Tsitsipas further stated that he is quite familiar with the ATP Finals format now, as this is his third time featuring in the season-ending event.

"Well, I know how the format works," he said. "I know how everything runs. You know, I'm pretty experienced here, I assume, having played three times so far."

Despite appearing twice at this event in the past, the Greek said he still gets just as excited about playing here as he did the first time. Not many players are used to the ATP Finals format because it isn't frequently used, but Tsitsipas likes it because it gives him opportunities to improve his game after every match.

"The feeling of playing here never gets old," the 23-year-old said. "I'm always the same kind of excited as I was at the very first time. It's a format that most of the players are not familiar with, because we don't get to play very often with round-robin rules, and, you know, sets can be kind of important, how many sets you win and how many you lose. I like it, because it gives me chances and I can improve and get better match by match."

The Greek is set to play Casper Ruud in his next round-robin match.