Nadal hails unbelievable Isner

Nadal: Forced to dig deep

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Rafael Nadal has hailed the "unbelievable potential" of John Isner after the world No.3 was taken to the wire by the American at the BNP Paribas Open in Indian Wells.

Nadal was forced to dig deep to book his place in the last eight before securing a 7-5 3-6 6-3 win in two hours 10 minutes over the giant Isner.

And the Spaniard was clearly relieved to set-up a quarter-final showdown with Tomas Berdych, who defeated Viktor Troicki of Serbia 6-1 6-3.

"Today was a really difficult match, so I know I have to play my best tennis," said Nadal.

"I did really well, I think. I only played a really bad game in the fourth game of the second set, but the rest of the match I'm very happy how I did.

"I think John is a big player, very difficult to play against him, and he has unbelievable potential. So for me it is a very important and very good victory."

Marcos Baghdatis failed to build on his victory over Roger Federer as he crashed out to 18th-seeded Spaniard Tommy Robredo, 7-5 0-6 6-4.

And second seed Novak Djokovic followed Federer in suffering a shock defeat as he lost 7-5-6-3 to 20th seed Ivan Ljubicic.

But despite the disappointment of defeat, Djokovic maintained he could take some positives from his efforts this week.

"I am not happy with the overall performance that I had in this tournament, because I know I could have played better and could have done better," he said.

"But under decent circumstances I still made it to the fourth round, which is quite okay."

Seventh-seeded American Andy Roddick is also through after battling to 7-6 (7-5) 6-4 victory over Jurgen Melzer, while Argentina's Juan Monaco will face Ljubicic after securing a 3-6 6-2 6-1 over Guillermo Garcia-Lopez.