Defending ATP Finals champion Daniil Medvedev maintained his winning streak in this year’s tournament but found the going tough against Alexander Zverev, eventually winning 6-3, 6-7 (3-7), 7-6 (8-6) in their Red Group clash on Tuesday.

Medvedev had won his opening match against Hubert Hurkacz while Zverev was given a walkover in his opener on Sunday against Italian Matteo Berrettini. Berrettini retired injured and then withdrew from the tournament on Tuesday.

The ATP said that first alternate Jannik Sinner will take compatriot Berrettini’s place.

The Russian world No.2, who won his first grand slam this year at the US Open, raced into a 3-0 lead in the first set by frequently coming to the net and looked like he would take a comfortable fifth straight victory over Zverev.

However, the German found some confidence in Turin to bring himself back into the contest, firing down 13 aces and taking the second set on a tie-break.

The pair could not be separated in the decider with neither able to break serve and both soaking up some heavy hitting. In the decisive tie-break, Zverev saved two match points but could only hit a backhand into the net on a third to give Medvedev his seventh straight win at the ATP Finals after two hours and 35 minutes.

Zverev, 24, faces Poland’s Hurkacz in his final round-robin match looking to clinch a place in the last four.

The Green Group resumes on Wednesday with Novak Djokovic facing Andrey Rublev and Stefanos Tsitsipas taking on Casper Ruud.

Tsitsipas loses

On Monday, Andrey Rublev began his campaign with a victory over Greek Stefanos Tsitsipas. Rublev beat world No.4 and 2019 champion Tsitsipas 6-4, 6-4, but the 24-year-old Russian was clearly not used to playing late after his group match was scheduled for 9pm local time in Turin.

“I never sleep during the day. I set the alarm for 6.00 pm and when I woke up, it was so dark,” he said.