Juan Martín del Potro confessed that he considered retiring in the darkest moments of what turned out to be a miracle 1-6, 2-6, 6-1, 7-6, 6-4 comeback over Dominic Thiem in the US Open fourth round.
But the 2009 champion at Flushing Meadows instead set up a re-match of his victorious final against Roger Federer as he played on through the effects of a fever which he first felt two days earlier.
"I was thinking to retire in the middle of the second set because I couldn't breathe, I couldn't move well. Dominic was dominating the match so easy," the Argentine said.
"But when we started the third set, I broke his serve very quickly and won the set in 20 minutes - the history changed a lot.
"I took all the energy from the fans. That's what I did in the end, just kept fighting. I didn't give up.I was ready to win the match from that moment."
Del Potro, whose career has been repeatedly interrupted by wrist surgeries and rehab, now finds himself facing Federer yet again in New York, with the Swiss leading their series 15-5 while winning the last three matches - including Miami in March.
"Of course, I admire him, everybody loves him. Is going to be interesting match for play, after eight years again in the central court," Del Potro said. "I know how to play if I want to win, but I will see how physically I feel after this battle. But always it's a pleasure to play the greatest guy on the history."