Britain's James Willstrop recorded one of the most impressive wins of his career when he beat Egypt's Mohamed Elshorbagy in a 122-minute five-game thriller in the Hong Kong Open.
Third seed Willstrop, 30, entered the quarter-final with a 9-3 head-to-head record over his 22-year-old opponent.
But it was Elshorbagy who started the brighter, edging the first two games.
Willstrop then fought back, clinching victory on his eighth match-ball after a marathon 39-minute decider.
The match was Willstrop's second longest in his 14-year career, five minutes short of a 127-minute semi-final epic against compatriot Nick Matthew in the 2010 Canary Wharf Classic.
"It was a really close match - we were very tightly matched," said former world number one Willstrop.
"It was so close all the way - no player had any dominance at any stage, which is very unusual as you usually get a phase where one player gets a lead but there was hardly any of that.
"I think we were both at the top of our games, both playing some quite brilliant - and tough - squash.
"I'm happy to have won the match - there are a lot of positive thoughts."
Willstrop will play surprise opponent Borja Golan after the Spaniard beat top seed and defending champion Ramy Ashour, who appeared to be struggling with a recurrence of the hamstring injury which ended his world title bid in November.
Ashour called it quits at 7-0 down in the final game, and Golan admitted: "When you respect a player like we all respect Ramy it is tough. He is such a talented player and that is the last way that I want to win a match.
"I hope he is soon on the court - but for a long time, not just a few tournaments."
The other semi-final sees fourth seed Matthew take on second seed Gregory Gaultier in a repeat of last month's World Championship final.
There was a shock in the women's event when world number two Laura Massaro of England lost 11-6 11-5 9-11 11-9 to Hong Kong's Annie Au.
Top seed and eight-time defending champion Nicol David beat Jenny Duncalf (Eng) 11-4 11-3 11-3, and goes on to face another English player, Alison Waters, in the last four.