Taylor Fritz kept a cool head against the furious Daniil Medvedev and won the opening match of the ATP Finals in straight sets.
American Fritz recorded his 50th win of the year by beating Medvedev 6-4 6-3 at the season-ending tournament in Turin, Italy.
Russian fourth seed Medvedev broke a racket in response to his poor serve and threw a second after a setback while on break point.
“I’m super happy with how I played today,” said Fritz, who reached his first Grand Slam final at the US Open in September.
Medvedev hit seven double faults in a tight opening set, including two back-to-back, to earn fifth seed Fritz a set point.
To cap off a disastrous service game, the Russian double-faulted again and reacted angrily to going behind by slamming his racket into his chair and the ground.
Early in the second set, Medvedev earned his first break point of the match, but hit his backhand return into the net.
Further break points went unconverted for both players before Fritz took advantage with his third, with a mishit lob landing on the line.
An irritated Medvedev was then given a point penalty after breaking a microphone on the court by throwing his racket.
As his behavior unfolded, he was booed by the crowd for his antics, which included holding his racket by the head while waiting for a serve.
“I get angry, frustrated. This time all at myself, at no one. Only at myself,” Medvedev said.
Fritz served out the match with ease, but said that despite his opponent’s behavior he could not rest until victory was confirmed.
“I had a feeling that at 5-3 he was going to reset and do his best to break me. I had to tell myself that he wasn’t just going to be done with the match,” he said.
“It’s sometimes very easy when someone does that to relax and think it’s done, and then you drop your level.
“I had to stay focused and play a good game because he was going to fight. I served a great game.”
Fritz and Medvedev are joined in the Ilie Nastase Group by Italy’s number one Jannik Sinner and Australia’s Alex de Minaur, who will play in the second round-robin match of the day from 7.30pm GMT.
Britain’s Henry Patten is also in action from 5pm as he and Finnish doubles partner Harri Heliovaara begin their campaign against second seeds Marcel Granollers of Spain and Argentine Horacio Zeballos.
Patten makes his debut at the tournament after he and Heliovaara won the Wimbledon title and finished as the seventh best team this season.
