Taylor Fritz kept his cool in the face of an irate Daniil Medvedev to win 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 racquet in response to his poor serving and threw a second after a stroke of bad luck while break point down.

“I’m super happy with how I played today,” said Fritz, who reached his first Grand Slam final at September’s US Open.

Medvedev hit seven double faults in a tight opening set, including two back-to-back to give fifth seed Fritz set point.

Capping a calamitous service game, the Russian double-faulted again, and reacted angrily to going behind by smashing his racquet against his seat and the ground.

At the start of the second set, Medvedev earned his first break point of the match but slammed his backhand return into the net.

Further break points went unconverted for both players before Fritz capitalised on his third, with a mis-hit lob that landed on the line.

An irritated Medvedev then received a point penalty after he broke a courtside microphone by throwing his racquet.

As his behaviour unravelled he was booed by the crowd for his antics, which included holding his racquet by its head as he waited to receive a serve.

“I get angry, frustrated. This time completely with myself, not with anyone. Just with myself,” said Medvedev.

Fritz easily served out the match to love but said despite his opponent’s conduct, he could not rest until the win was confirmed.

“I felt at 5-3 he was going to reset and try as hard as he could to break me, I had to tell myself he’s not going to just be done with the match,” he said.

“It’s very easy sometimes when someone’s doing that to relax and think they’re just going to be 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 world number one Jannik Sinner and Alex de Minaur of Australia, who will play in the second round-robin match of the day from 19:30 GMT.

Britain’s Henry Patten is also in action from 17:00, as he and Finnish doubles partner Harri Heliovaara start their campaign against the second seeds, Marcel Granollers of Spain and Argentine Horacio Zeballos.

Patten is making his debut at the tournament, after he and Heliovaara won the Wimbledon title and finished as the seventh-best team this season.