Rafael Nadal admits he "suffered" after playing his longest-ever match at the US Open against Dominic Thiem on Tuesday night.
The world No 1 recovered from a first-set bagel to defeat Thiem and reach the US Open semi-finals following another late-night classic in New York.
Twenty-four hours after Roger Federer fell to John Millman, his old rival avoided following him out of the tournament, but only just, completing a 0-6 6-4 7-5 6-7 (4-7) 7-6 (7-5) victory in a gripping four hours and 49 minutes, concluding at 2.03am.
Ninth seed Thiem became the first player since Andy Roddick in 2004 to win a love set against Nadal in New York but the defending champion once again dug deep to come out on top of a gruelling battle played in more punishing humidity.
Thiem, the only man to beat Nadal on clay for the last two seasons, blasted 13 winners, made only two unforced errors and allowed Nadal just seven points in winning an extraordinary opening set.
It was only the fourth time in his long Grand Slam history that Nadal had lost a set 6-0 and just the third time at any level in nearly seven years.
"When these things happen, normally I am not the guy that looks at the string or looks at the box or looks at the racket," said Nadal.
"I am the guy to look at myself. I needed to move forward, to change that dynamic, and I did. But the first step to change that dynamic is not to find an excuse on the racket or on the string or on something that is not the truth. The only truth is that you have to do things better to be able to fight for the point and fight for the match."
After seeing off the first top-20 player he had faced at the US Open since 2013, the Spaniard added: "I suffered, that's the right word. I said to Dominic I am sorry. He's a great guy, a close friend who will have many more opportunities to win the big titles. He has a great attitude and is a great fighter."
Thiem said his epic defeat to close friend Nadal will stay with him forever, saying: "It's going to be stuck in my mind forever. Forever I'm going to remember this match, for sure.
"Tennis is cruel sometimes because I think this match didn't really deserve a loser. But there has to be one.
"It ended up in the fifth set tiebreaker, there it's 50/50. He made one more point than me."
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