Swiss star Roger Federer has revealed that players using different tennis balls at various events doesn’t help their bodies and can be a reason for injuries, Tennis World USA report.

The 20-time Grand Slam champion recently suffered a shock defeat to Australian John Millman in the fourth round of the US Open.

Federer took the first set 6-3, however, Millman, who previously had never came out on top against a top-10 player, won the next three 7-5 7-6 7-6.

Alex Pantling/Getty Images Sport

Since Federer’s shock loss, the 37-year-old has been questioned about the state of tennis balls across the course of the season.

Each of the four Grand Slams next season are set to use a different ball, and Federer has admitted that he has given up on asking the sporting authorities to use the same ball across the season.

It’s been an ongoing battle on the tour trying to fix that.

It’s just too different. To be quite honest, I’ve given up on telling the tour we should play with same balls everywhere we can. There are different manufacturers, and then obviously they make their own deals with certain tournaments.

Then some have a three‑year deal, a ten‑year deal, and you’re just never going to get it right, I don’t think. It’s not like we’re playing with stones one week and then with tennis balls the next. I know there are differences and your shoulder starts to hurt from time to time, but that’s where a healthy lifestyle and rehab and all that stuff is important.

I think we’re doing okay considering. If you look at all the wear and tear, I think the professional tennis athletes are doing well considering.

For 2019, the Australian Open are scheduled to use Dunlop, the French Open are set to use Babolat, Wimbledon will stick with Slazenger and the US Open will be using Wilson.