ROTTERDAM (AFP) - Rafael Nadal defeated world number 490 Grigor Dimitrov 7-5, 3-6, 6-2 on Thursday to reach the Rotterdam Open quarter-finals, but the Bulgarian teenager demonstrated his exciting potential as a future star. World number one Nadal had plenty of problems with the 17-year-old junior Wimbledon and US Open winner who broke the newly-crowned Australian Open champion in the eighth game of the second set on his way to levelling the match. But Nadal, who has struggled all week on the ultra-fast court here, quickly recovered his poise to reach the last eight although Dimitrov twice had chances in the final set to grab a break before running out of steam. "He is heading to the top 10, for sure," said the Spaniard, who broke on seven of 12 chances in the tight second round contest. "It was a really tough match and I had to work to win it." Nadal, who now faces French seventh seed Jo-Wilfried Tsonga for a semi-final spot, said Dimitrov reminded him of his own early days on the tour. "I remember when I was 17 and beat (Roger) Federer in Miami. The motivation is great and you have nothing to lose. It was the same for me then." Andy Murray overcame a raft of errors in a hit-or-miss opening set before posting a gruelling 7-6 (7/4), 7-5 win over Italy's Andreas Seppi. The second seeded Scot struggled to impose himself in the first set which dragged on for nearly an hour with the world number four needing seven set points, spread over four games, to finally take the lead. Things improved slightly in the second set with Murray and 36th-ranked Seppi trading breaks in the fourth and fifth games. Murray benefitted from a Seppi double-fault to take a 6-5 lead and finally got off court on his second match point and after an hour and three-quarters. "There were a lot of errors from both sides in the first set," said Murray, who lost in the first round here a year ago. "The standard was not good. Both of us started playing better and by the second set it was really tough. He hits flat and hard and moves really well." Murray will next face French lucky loser Marc Gicquel, who defeated compatriot Paul-Henri Mathieu 6-4, 6-3. French fifth seed Gael Monfils, who put out compatriot and defending champion Michael Llodra 6-4, 6-4, will tackle fellow Frenchman Julien Benneteau who booked his last-eight place on Wednesday with an upset win against Russian third seed Nikloay Davydenko. Croatia's Mario Ancic, a runner-up at Zagreb last weekend, beat French fourth seed Gilles Simon 6-4, 3-6, 6-3. Ancic has had a troubled few seasons with illness and injury but feels he is now back on his feet. His defeat of Simon was only his 13th victory against 39 losses when facing top ten opponents. Against the elite, the win was only his second since 2007. "This is unbelievable," said the 28th ranked Croatian. "Gilles is a top player and they are always very difficult to beat." Ancic next faces Russian Mikhail Youzhny.