In the longest match of the day, experienced second seed Alister Walker held off a determined challenge from Egyptian teenager Amr Khaled Khalifa to reach the quarter-finals of the 3 Rivers Capital Pittsburgh Open, the PSA World Tour International 25 squash event in its third successive year at Rivers Club in Pittsburgh, USA.
Walker, the world No20 from Botswana fresh from his title success in the Dayton Open in Ohio last week, fought back from 1-6 down to take the first game.
Khalifa, the 18-year-old former world junior champion from Cairo, built another 6-1 lead in the second, and this time held on to draw level.
"But the first two games seemed to wear Khalifa down," said tournament organiser Steven Baicker-McKee. "The experience, skill, and fitness of Walker came through in the next two games, where the veteran seemed in control."
Walker's 11-9, 8-11, 11-4, 11-4 victory in 78 minutes takes the 29-year-old through to the quarter-finals where he will face Chris Simpson, a 12-10, 10-12, 11-4, 11-6 winner over fellow Englishman and qualifier Joel Hinds.
English favourite Adrian Grant cruised into the last eight after despatching compatriot Jaymie Haycocks, a qualifier, 11-5, 11-4, 11-5.
RESULTS: PSA International 25 3 Rivers Capital Pittsburgh Open, Pittsburgh, USA
 Adrian Grant (ENG) bt [Q] Jaymie Haycocks (ENG) 11-5, 11-4, 11-5 (33m)
Henrik Mustonen (FIN) bt Stephane Galifi (ITA) 11-7, 11-5, 11-6 (29m)
Campbell Grayson (NZL) bt Scott Arnold (AUS) 11-6, 11-7, 11-8 (44m)
 Shahier Razik (CAN) bt Arturo Salazar (MEX) 11-7, 11-5, 6-1 ret. (21m)
 Ryan Cuskelly (AUS) bt [Q] Olivier Pett (ENG) 9-11, 11-5, 9-11, 11-5, 11-4 (74m)
Cesar Salazar (MEX) bt [Q] Eric Galvez (MEX) 11-4, 11-7, 11-7 (35m)
Chris Simpson (ENG) bt [Q] Joel Hinds (ENG) 12-10, 10-12, 11-4, 11-6 (65m)
 Alister Walker (BOT) bt Amr Khaled Khalifa (EGY) 11-9, 8-11, 11-4, 11-4 (78m)
 Adrian Grant (ENG) v Henrik Mustonen (FIN)
 Shahier Razik (CAN) v Campbell Grayson (NZL)
 Ryan Cuskelly (AUS) v Cesar Salazar (MEX)
 Alister Walker (BOT) v Chris Simpson (ENG)
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