The small furry objects that are the focus of every tennis player's energy are spinning the stars at the ATP finals into a fury and leaving them deflated.

"The balls are a big problem", said world No.2 Alexander Zverev.

Many of the top players say all the brands have deteriorated and most dislike playing with different makes of ball from one tournament to the next.

At the ATP finals in Turin, there has not been a press conference at which the subject has not popped up.

The ATP, which runs the men's tour, has had a partnership agreement with Dunlop since 2019 in a deal until 2028.

But the ATP said the Japanese manufacturer's balls are only used "by around half of the tournaments on the circuit," including four Masters 1000 events and these finals.

The four Grand Slam tournaments, which consume over 50,000 balls each year and provide manufacturers with much sought-after exposure, have separate deals.

The Australian Open uses Dunlop, the French Open and US Open have deals with the American manufacturer Wilson, and Wimbledon with the British company Slazenger.

"If you have a stretch of four tournaments in the same continent and they use four different balls, it can be difficult and challenging," said Casper Ruud after his opening victory over Carlos Alcaraz.

- 'The balls die' -

The most outspoken critic is the hot-tempered world No.4 Daniil Medvedev who, recently in Shanghai, pretended to spit on one ball and wipe his backside with another.

"The balls die in air," the Russian said after his victory over Australian Alex De Minaur on Tuesday.

"When I return from five meters back, at the end the ball literally stops, so the guy has time to attack me."

"Everyone can stay in the rally now."

Zverev, who is on the ATP player advisory council, said the pandemic was partly to blame.

"They've gotten a lot slower," The German said on Monday after his victory over Andrey Rublev.

"Because of Covid, the companies tried to cut costs and they're using a different rubber material now. They're using a different material for the tennis balls, which makes the tennis balls between 30 per cent and 60 per cent slower on average."

"They don't last as long, they change from one batch to another, they lint more," he added.

Russia's Daniil Medvedev eyes the ball to hit a return to Australia's Alex De Minaur during their match at the ATP Finals on Tuesday. Photo: AFP

Zverev said it was natural that balls fluff up in the seven games before they are changed but now they deflate.

"The air and the pressure leaves the tennis ball because of the material. The material doesn't keep it inside," he said, adding "the pressure of the tennis ball drops drastically."

- 'Like a shuttlecock' -

He said matches felt a bit like badminton.

"They're a little bit like a shuttlecock. They fly very fast through the air the first two, three meters, then they just slow down. There's nothing that keeps the ball alive, which was very different about five, six years ago," he said.

Zverev also blamed the balls for injuries.

"That's why a lot of players now have elbow issues. A lot of players have wrist issues," he said. "That was not the case about 10, 15 years ago."

Ruud said switching ball brands between tournaments is "the beauty of the game. It's nice because you'll have different winners.'

"If you just stick to one ball, it would be in a way a bit unfair for whoever likes the Tecnifibre ball," Ruud said.

"It will give less chances to a guy who prefers a Wilson over a Dunlop ball."