Wimbledon 2017: 'Big Four' still the ones to beat, says Juan Martin del Potro

Juan Martin del Potro of Argentina in action during a training session prior to the Wimbledon Championships at the All England Lawn Tennis Club, in London, Britain, July 2, 2017.

The "Big Four" of men's tennis remain the players to beat at Wimbledon, said former US Open champion Juan Martin del Potro, as this year's tournament at the All England Club gets under way.

Since 2003, Roger Federer has taken seven titles at the grass-court grand slam followed by Novak Djokovic's three, while Andy Murray and Rafa Nadal have claimed two each.

The quartet have also been named as the top four seeds for the first time since 2014, though defending champion Murray and Djokovic have had mixed seasons.

"They have returned to be the 'Fantastic Four', as they have been throughout their careers," Argentine del Potro told the ATP World Tour website. "I think it's something that appeals to every tennis fan.

"I've always played good tennis at Wimbledon ... It is a tournament that always brings surprises in the first rounds and I think it's also nice that we have the same top seeds that we had in 2009. They are at an excellent level."

READ MORE:

• Five games to watch on Day 1
• Five to take advantage of Williams' absence

Federer warned on Saturday that he and the rest of the big four were going to be as tough to beat as ever at this year's event.

Seeded 29th, Del Potro has struggled with persistent wrist injuries in recent years. But the Argentine, who won the US Open in 2009 and reached the Wimbledon semi-finals in 2013, is still hopeful of rising back up the rankings.

"I'm still there with an acceptable position [in the ATP Rankings]. I'm still improving in my comeback. It's a little out of the ordinary to what I'm used to in my career, but I'm calm and I know that my level will return," he said.

He faces Australia's Thanasi Kokkinakis in the first round on Tuesday.