Del Potro and Fernando Gonzalez Advances to Quarter Finals of US Open by Defeating Their Respective Opponents Ferrero and Tsonga

Del Potro's big serve was the foundation of his victory, with the Argentine serving 22 aces on his way to victory, without ever being broken.

He will play Marin Cilic next after the big-serving Croatian beat Andy Murray.

Chile's Fernando Gonzalez beat seventh seed Jo-Wilfried Tsonga of France in a pulsating match 3-6 6-3 7-6 (7-3) 6-4.

The 11th seed will face the winner of the late match between Rafael Nadal and Gael Monfils.

Defending champion Roger Federer, Robin Soderling, Novak Djokovic and Fernando Verdasco are already through to the last eight at Flushing Meadows.

Del Potro lost to Murray in the quarter-finals last year but has since risen to sixth in the rankings lost to Federer in five sets in the French Open semi-finals.

"Being in the quarters, it's important," said Del Potro. "But it's a big difference past the quarters to the semis and then through to the finals.

"I was so close in the French Open to reach the final and to beat Roger. Here I have another chance to be better and I will try to go the semis. If I lose I still had a good tournament."

The 20-year-old's improved serve has been a major factor in his success, along with his power off the ground, and he made 44 winners as he dominated Ferrero.

"When you play somebody like this, you feel a lot of pressure with your service games," Ferrero said afterwards.

"I think he's playing a level to win a Grand Slam. I think he can play against anybody here. He has to play against Cilic right now, I think this is a chance for him to get into the semis."