Murray through to last eight

Andy Murray defeated Kristian Pless 6-3 7-6 (7-4) at the Morgan Keegan Championships in Memphis to book his place in the quarter-finals.

The Scottish world number 13 could meet Andy Roddick in the semis after defeating Pless for the second time in a week.

The 19-year-old, who retained his SAP Open title in San Jose last week - beating Pless along the way, will face Austria's Stefan Koubek in the last eight.

"I would love to win my next match," said Murray. "My longest win streak last year was seven and I'd like to try to go one better and put myself in a position where I have a chance of winning a tournament.

"I feel like I'm hitting the ball better. I just need to play a little bit more aggressively on the break points. I felt much more comfortable out there."

Top seed Roddick overcame German Benjamin Becker in straight sets and will face Chinese Tapei player Yen-Hsun Lu in the last eight.

It was a good day for the Americans as fourth seed Mardy Fish also progressed thanks to a 6-1 7-6 (11-9) victory over Juan Martin Del Potro. His next opponent is Russian qualifier Teimuraz Gabashvili.

Unseeded Sam Querrey continued to impress after toppling seventh-seeded Frenchman Julien Benneteau 6-3 6-4.

The 19-year-old American will next meet second seed Tommy Haas, a 7-6 (7/2) 7-6 (7/5) winner against Amer Delic.