London - Juan Martin del Potro doubted on Friday whether he would ever return to the peak of tennis despite stunning fourth seed Stan Wawrinka to reach the Wimbledon last-32.
The towering Argentine was number four in the world and a US Open champion in 2009 before four wrist surgeries - including three in the last two years - pushed him to the brink of quitting.
The world number 165, playing in his first Grand Slam tournament since the 2014 Australian Open, clinched a 3-6, 6-3, 7-6 (7/2), 6-3 victory over Wawrinka under the Centre Court roof.
By the end of it, the 27-year-old was shaking with emotion.
But he worries that his once-feared backhand is now so weakened by surgery that he will never recapture the form that saw him memorably defeat Roger Federer to capture his first major in New York seven years ago.
"I still need time to feel 100 percent with my wrist. Sometimes I am scared to hit harder with my backhand," he said.
"It was really tough to come back on the sport after my third one. But now I'm enjoying tennis again.
"I don't know if I can be in the top positions again. But if not, I will be happy just to be playing tennis."
'I FEEL ALIVE AGAIN'
Del Potro was a semi-finalist on his last appearance at Wimbledon in 2013 where he lost a memorable five-setter against Novak Djokovic.
He goes on to face French 32nd seed Lucas Pouille for a spot in the last-16.
"I feel alive again. After sitting at home for two years, this feels like a second or third career," added Del Potro.
The Argentine added that despite making the third round, he was already concentrating on 2017 as the year which will really test his powers of recovery.
"Every single day, every week is getting better. If I finish healthy this year, I will do a good preparation for the next season, and hopefully I can be playing harder in all my shots," said Del Potro after facing just his second top-10 opponent in three years.
"The doctor says I can do it. I think just two or three months ago, I only played slices, and now sometimes I hit with top spin. On the returns, I can go harder. That is a small thing to me, but it's important."
Wawrinka, a quarter-finalist in 2014 and 2015, fired 47 winners past Del Potro but was undone by 48 unforced errors.
However, the Swiss star said it was good for the sport to have the Argentine back in business.
"We are happy that he's back. He's a great guy off the court. He's amazing player on the court. He's big champion," said Wawrinka.