Defending champion Nick Matthew battled back from two-games down and saved three match balls to avoid a shock exit to Spain's Borja Golan at the Professional Squash Association (PSA) Windy City Open in Chicago.
The 35-year-old Englishman, a three-time world champion, had won all six games he had previously played against his opponent but struggled to get going at the University Club.
He dug deep, however, and eventually sealed a punishing 10-12, 9-11, 11-3, 13-11, 14-12 victory in the second round clash.
"I feel like a bit like I’ve won the tournament right now,” said Matthew.
“It is mad that that was only a second round match.
“In the first two games, especially the first game, it was the best I’ve ever seen him play - I don’t think I played badly but I was 2-0 down.
“I won here last year and the thought of losing second round was driving me on - I just kept fighting and fighting - sometimes you just have to do whatever you can to win.
"I went all the way to plan Z today.”
Matthew will now play Egypt's Tarek Momen in the quarter finals, after he beat world junior champion Diego Elias of Peru 8-11, 11-6, 11-7, 11-7.
Another Egyptian, Omar Mossad, beat Saurav Ghosal of India 13-15, 11-1, 11-7, 11-1 to set up a last eight encounter with France's Mathieu Castagnet who ousted England's Daryl Selby 11-7, 11-5, 3-11, 11-9.
In the women's competition, number two seed Raneem El Welily of Egypt advanced to the quarter-finals as she saw off Annie Au of Hong Kong 15-13, 7-11, 11-8, 11-7.
Her prize is a clash with compatriot Nouran Gohar, who knocked out England's Jenny Duncalf 11-9, 11-9, 11-4.
France's Camille Serme came through against Hong Kong's Joey Chan, 11-6, 11-5, 11-2, and will meet American Amanda Sobhy, who saw off New Zealander Joelle King 11-6, 11-4, 11-5.
Action will continue in Chicago tomorrow.