Del Potro: ‘Big Four’ are still the favourites

Former U.S. Open champion Juan Martin del Potro says the men's 'big four' of tennis are still the ones to beat as Wimbledon kicks off on Monday.

The slam has been dominated by four players, Roger Federer with seven titles and then Novak Djokovic with three, Andy Murray and Rafa Nadal with two each.

The four players have also been given the top four seedings at the grass court tournament and Del Potro says it's amazing that the top four seeds are the same that were in 2009.

"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."

Having struggled with wrist injuries over the last few years, the 29th-seeded Del Potro, who faces Australia's Thanasi Kokkinakis in the first round on Tuesday, said he hoped to keep improving his ranking. 

"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," del Potro added.