London - With his clubbing flat forehand and big serve, former US Open champion Juan Martin del Potro has all the tools to provide Rafa Nadal with his first stern test in the defence of his Wimbledon crown on Monday.
The giant Argentine, who stands an imposing 1.98 metres tall, climbed to fourth in the world rankings after his US Open triumph in 2009 before a wrist injury that required surgery forced him to miss almost all of last year.
But the 22-year-old has worked his way back to form and fitness and has an all-round game with the potential to derail Nadal's bid for an 11th grand slam title.
"I think he has a good serve and very good shots from the baseline, I think he's a complete player," Nadal, who is chasing a third Wimbledon crown, told reporters after easing past Luxembourg's Gilles Muller on Saturday.
"It is always is a big challenge to play against him. He's a very tough opponent and one of the best players of the world.
"His ranking is much better than what the ranking says today. His level is much better than what the ranking says today.
"If we talk about level, when he's healthy, he's a top five player. I'm unlucky to have to play against Del Potro in the round of 16. But that's what it is, and I have to be playing my best tennis to try to win."
The Argentine now finds himself edging back towards the world's top 20 after an arduous rehabilitation and he is quick to play down expectations that he can swiftly rediscover the form that enabled him to beat Roger Federer in the final at Flushing Meadows two years ago.
"It's not easy to be top five, but I'm improving my game every day," he told reporters after booking his place in the fourth round with a straight sets-win over French No 15 seed Gilles Simon.
"That's a good sign for the future. But, of course, I want to be at the top as soon as possible. But it's a long, long road."
Nadal's progress into the fourth round has been plain sailing with none of his opening three opponents taking a set off the Spanish matador.
On top of his US Open triumph, Del Potro has reached the French Open semi-finals and the quarter-finals in Australia, but this is his first foray past the second round at Wimbledon.
"Of course on Monday I play against the best player in the world in this moment," he added.
"Against him you have to play unbelievable tennis. You have to play everything perfectly, and then maybe, you have a little chance.
"But it's my first time in fourth round in Wimbledon and I want to treasure this moment."