RESULTS: PSA World Series North American Open, Richmond, Virginia, USA

Quarter-finals:
[1] Nick Matthew (ENG) bt David Palmer (AUS) 8-9 ret. (23m)
[4] Amr Shabana (EGY) bt Mohd Azlan Iskandar (MAS) 11-7, 6-11, 12-10, 12-10 (48m)
[3] James Willstrop (ENG) bt [6] Peter Barker (ENG) 7-11, 11-4, 11-4, 11-5 (49m)
[2] Ramy Ashour (EGY) bt [5] Gregory Gaultier (FRA) 11-5, 9-11, 11-4, 6-11, 11-8 (68m)

England's world champion Nick Matthew was given a walkover into the semi-finals of the $115,000 North American Open when his Australian opponent David Palmer was forced to retire through injury.

Matthew, the Sheffield-based world No1, was trailing 8-9 in a tense and physical opening game when the two players collided in mid-court as Palmer tried to chase a ball into the back left corner.

After lengthy treatment to a twisted ankle, the 34-year-old US-based veteran announced that he could not continue play in this PSA World Series event, the second of the year, at the Westwood Club in Richmond, Virginia.

"I have another tournament coming up soon and it would be silly to risk it," said Palmer, the former world number one and world champion. "The ankle swelled up really badly. It's a shame because Nick and I were both playing well and it was shaping up to be a great match."

Top seed Matthew, the reigning NAO champion, meets Amr Shabana in the semi-finals after the No4 seed overcame Malaysian Mohd Azlan Iskandar in a wonderful match full of attacking squash.

It was so tight that Shabana needed to squeeze home in two tie-breaks before winning 11-7, 6-11, 12-10, 12-10 in 48 minutes of brilliant shot-making and phenomenal retrieving.

Third seed James Willstrop maintained his unbeaten record against England team-mate Peter Barker. In their 12th PSA Tour meeting, Willstrop recovered after losing the first game to win 7-11, 11-4, 11-4, 11-5 in 49 minutes.

It was a stylish, measured performance and Willstrop, the world No4 from Leeds, will need a repeat performance in the semi-finals against Ramy Ashour.

The Egyptian genius overcame Gregory Gaultier in a spectacular finale to the evening.

Gaultier played superbly but Ashour's speed around the court and a succession of deadly crosscourt kill shots proved the decisive factors.

After clinching a 68-minute victory, with a scoreline of 11-5, 9-11, 11-4, 6-11, 11-8, Ashour acknowledged the contribution of his opponent. "Greg has been out of action with an injury for a long time since the World Open and he is back playing better than he was before," said the world No2 from Cairo.

"That's why I needed to be so fast, just to get the ball back. He was playing incredible squash and I am very happy and relieved to be through to the semi-finals against James. That should be another great match."

Semi-final line-up:
[1] Nick Matthew (ENG) v [4] Amr Shabana (EGY)
[2] Ramy Ashour (EGY) v [3] James Willstrop (ENG)