Argentina's Juan Martin del Potro returned to see off Frenchman Gilles Simon on Tuesday and reach the Wimbledon quarter-finals for the second time, but it was desperately hard work.
The fifth seed had led by two sets on Monday but Simon grabbed the third set before fading light ended play.
With world number one Rafael Nadal waiting for the winner, Tuesday's fourth set, played in much cooler conditions than the first three the day before, turned into a mini-epic before Del Potro eventually prevailed 7-6(1), 7-6(5), 5-7, 7-6(5).
Del Potro looked flat as he was broken to trail 3-1 but he clawed his way back to lead 5-4 with his serve to come.
He looked on the brink of victory when he moved 40-15 ahead but both match points vanished, the second with a double-fault.
Simon failed to convert a break point, then a third match point for Del Potro ended with him netting a forehand.
The 33-year-old Simon saved a fourth match point when he threw the kitchen sink at a forehand return and the world number 53 eventually took his fourth break point to level at 5-5.
The next two games went with serve and the match was well into its fifth hour when the tiebreak began.
Del Potro trailed 1-3 but at 5-5 he fired down a swinging ace to reach match point number five and this time Simon cracked, netting a backhand to the relief of the Argetine who roared his approval.
Ostapenko blasts past Cibulkova to reach semis
Jelena Ostapenko became the first Latvian to reach the Wimbledon singles semi-finals after she subdued Slovakia's Dominika Cibulkova 7-5, 6-4 on Tuesday.
After more than a week of sizzling 30 degrees Celsius temperatures, the players struggled to find their range on a chilly and blustery Court One, where the 'feels like' temperature dipped to around the 14 degrees mark.
Four of the first five games went against serve before 12th seed Ostapenko's game finally caught fire in the 11th game when she broke Cibulkova to love with a blazing backhand down-the-line winner.
Two successive aces, clocked at 103 and 106 mph, gave the 21-year-old the first set and the 2017 French Open champion tightened her grip on the contest when she ended another flurry of breaks to go 4-2 up in the second.
Cibulkova did her best to try and hang on but the Slovakian was left chasing shadows as Ostapenko blasted a backhand winner on her first match point to reach the last four without dropping a set in this year's tournament.
She will meet German 11th seed Angelique Kerber for a place in Saturday's final.