World number one Rafael Nadal has tipped Juan Martin del Potro for more Grand Slam glory after he was handed a tennis lesson by the Argentine in their Shanghai Masters semi-final on Saturday.
The 25-year-old prevailed 6-2, 6-4 against the shell-shocked Spaniard in a devastating display of power hitting to set up a final against top seed Novak Djokovic.
And Nadal, who returned to the top of the rankings this week after a stunning season, said if Del Potro could repeat the form he showed in their Shanghai battle, he could smash the monopoly of the "Big Four" on the majors.
The giant Argentine, who beat Federer in the 2009 US Open final, is the only player since 2005 to win a Grand Slam aside from Nadal, Federer, Djokovic and Andy Murray, but he has not reached another final since.
"If he plays similar to this level, for sure he's one of the biggest candidates to win a Grand Slam tournament. He's able to do it. I'm sure he will win more," said Nadal, who has won 13 major titles, just four behind Federer's record of 17.
"It is true that the last three years he played well, but he didn't arrive to this level. So it is great to see him play again at this very, very high level. At the end it is good to have players who have the potential to play at this unbelievable level."
Del Potro himself, who qualified for next month's World Tour Finals in London with his victory, said to improve from his current ranking of number five would be tough.
"Not many players have the chance to beat them (the top players)," he said. "I always believe in myself. I always believe in my game. It could be my biggest challenge of my career, getting closer to the top positions.
"But also I am very clear they are playing so solid for a year, and I played good tournaments. I think there is the difference between the top guys and me or the rest of the players.
"I have to be playing at this level for many, many tournaments in a row, or in important tournaments."
Nadal himself has had a sensational year, winning 10 titles including the French Open and US Open after seven months out with a left knee injury.
The Spaniard was sanguine about his sobering defeat, admitting he had lost to the better player on the day.
"Today was one of these days," said the 27-year-old. "The positive thing is I fought during the whole match with the right attitude, in my opinion. If he went down a little bit, I was going to be there fighting for the match.
"When there are days like this, the only thing you can do is to congratulate your opponent."
"I consider my level this week very high," he added. "Yesterday was a great victory for me. If I am able to keep playing at this level, I am confident that I will keep having positive results. Not everybody is going to play like he did tonight."
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