Second seed Juan Martin Del Potro said he's not envious of the world top four as the big Argentine reached the Rotterdam quarter-finals Thursday with a 7-6 (7/5), 6-3 defeat of qualifier Ernests Gulbis.
"I know that I can improve," said the seventh-ranked 2009 US Open champion, who faces Jarkko Nieminen in the last eight after the Finn dispatched German qualifier Matthias Bachinger 6-3, 5-7, 6-3.
"But the top four are there for a reason, they are playing better than me, I know that I can beat them, but I need to improve my level. That's what I'm working on, like trying to come to the net more.
"Right now, I'm happy with my ranking, I'm not frustrated."
Del Potro, who lost the final in Rotterdam a year ago to Roger Federer, needed just over 90 minutes to beat Latvia's Gulbis, who once stood inside the top 30 before falling to his current 132.
"It was a really tough match, he's a strong player," said Del Potro. "I was a bit lucky in the (first-set tiebreaker). Then in the second set I improved my game and closed it out."
Marcos Baghdatis handed Frenchman Richard Gasquet only his second loss of the season as the Cypriot scored a 6-4, 6-4 win to reach the quarter-finals.
Gasquet lined up in Rotterdam as the fourth seed, having already won two tour titles this season and boasting an unbeaten record apart from a defeat to compatriot Jo-Wilfried Tsonga at the Australian Open.
But the world number 10 never got going against Baghdatis, who had also beaten him at the Olympics last year.
"Richard was probably tired, he's played a lot of tennis this season," said Baghdatis, in reference to Gasquet's run to victory in Montpellier last week.
Baghdatis won in 76 minutes, with nine aces and two breaks of serve, and will now face Bulgarian Grigor Dimitrov on Friday.
"He's a very talented player, he beat me 7-6 in the third set at Brisbane in January). He can play well and has a great future, I don't think he has any limits," said Baghdatis.