This event isn't Sinner's debut at the ATP Finals because he played before as an alternate, but it is the first time he's there as a Top 8 player. He's been utterly sensational all week long, winning all three of his matches in the group stage and adding the fourth win in the semi-final.
Sinner and Medvedev played two great matches in the last two months, with the Italian winning both. He bested the Russian in the China Open final and then in the Vienna Open final and now bested him again for another final.
The match opened with Medvedev being overly aggressive, attacking the Italian with a lot of deep balls. Sinner was a bit surprised but navigated that well. Not long after that, Medvedev played a bad game to basically give away his serve, which proved his undoing in the opening set.
From there, Sinner cruised easily, dropping only two points on his serve. Medvedev wasn't bad at all, except for that one game. He would continue playing well in the second set and dominating on his serve, as Sinner didn't see a single break point in the entire set.
He, too, managed to win all of his service games, so we went into a tiebreak where Medvedev had more momentum. He took it behind really strong play from the baseline. He outhit Sinner 19-5 in winners in that set, which was the idea.
From the start, the Russian showed an idea of playing more attacking, but it didn't work all the time. It didn't work at all in the final set as he served poorly, which opened Pandora's box.
Sinner smashed him from the baseline as Medvedev grew increasingly frustrated. The final score was 6-3 6-7(4) 6-1 for the Italian who finished with 10 aces and 28 winners.