Fritz gets ATP Finals started with first win over meltdown Medvedev
Medvedev, who was the ATP Finals champion in 2020 and runner-up the following year, lost his composure after a string of double faults in the first set as Fritz beat the Russian for the first time in his career.
The victory was also the 50th for US Open finalist Fritz in 2024 and his eighth top-10 win of the season.
"I definitely felt like at 5-3 (in the second set) he was going to reset and try as hard as he could to break me and I just had to kind of tell myself, 'He's not going to just be done with the match'," Fritz said.
"It's very easy sometimes when someone's doing that to kind of relax and think that they're just going to be done and then you drop your level.
"I just had to try to tell myself to stay focused at 5-3 and play a really good game because he was going to fight for that game. Luckily, I served a great game."
The opening set went with serve without a single break point until the final game, with Fritz especially dominant on his first serve while Medvedev struggled with his second serve.
But with Fritz leading 5-4, Medvedev won a long rally with a beautiful drop shot before he imploded and served three double faults to hand the set to his American opponent.
Medvedev was so incensed that he smashed his racket on the ground as he finished the set with seven double faults.
The Russian soon lost his composure again in the second set and began to unravel, breaking a microphone with his racket while he was also given a point penalty.
Medvedev kept pushing his luck and tested the chair umpire's patience by continually throwing his racket up in the air and dropping it. He also faced a Fritz serve holding the racket by its head as the Turin crowd began to whistle and jeer.
"I get angry, frustrated. This time completely with myself, not with anyone. Just with myself," Medvedev told reporters.
"I was like, 'Whatever, I lost the match. I don't care'. I mean, you have to finish the match. You cannot withdraw, no? I just finished the match."
Fritz eventually put Medvedev out of his misery when he served to love in the final game.
"I really want to make it out of the group stage. Let's say I'm putting more expectation on myself to do better, I think I'm just a better player," Fritz added.
World number one Jannik Sinner faces Alex de Minaur later on Sunday in the day's other group match.