LONDON (CNN) – John Isner waited a lot longer than his famed marathon encounter against Nicolas Mahut to finally make a Wimbledon quarterfinal. But it is a case of better late than never for the towering American.

On Wimbledon’s unique ‘Manic Monday’ — all 32 players remaining in singles were on the schedule — Isner beat Greece’s budding star Stefanos Tsitsipas 6-4 7-6 (10-8) 7-6 (7-4) to make the last eight in still steamy southwest London. “I’m very happy to be in the quarters,” Isner told reporters. “Feeling good. Definitely confident that I can keep going.

Eight years ago, Isner outlasted Mahut 70-68 in a fifth set in an encounter that took three days to complete. It was, by far, the longest match in tennis history. A year later, Isner reached his first grand slam quarterfinal in New York. But continued success at majors didn’t follow.

The 33-year-old pro has suffered his share of heartbreak, entering this Wimbledon with a 4-9 record in fifth sets since the start of 2012. Almost half of those losses went past 12 games in the fifth, including three grand slams, where there are no final-set tiebreaks.

Twelve months ago at Wimbledon, Isner was felled by the diminutive Dudi Sela in, yes, five sets.

“Certainly this tournament, since that long match, has sort of been a house of horrors for me,” the American added. “I’ve lost a lot of close ones since that match in 2010, a lot of very, very close ones, a lot of deep five-set matches, third round especially.”

“When you have left this tournament the last nine, 10 years pretty disappointed with my result, gone home sort of hanging my head a little bit,” said Isner. “But not the case this year.”

John Isner

John Isner celebrates after beating Stefanos Tsitsipas in their fourth-round match on the seventh day of Wimbledon in London on July 9, 2018. (credit: BEN STANSALL/AFP/Getty Images)

The ninth seed also moved a step closer to a potential semifinal with Roger Federer — whose comfortable win over Adrian Mannarino means that the Swiss hasn’t lost at SW19 since the 2016 semifinals. Rafael Nadal ended his six-year Wimbledon quarterfinal drought as well.

If Isner does reach the semifinals on Friday, he would “love” for President Donald Trump to watch him. Trump is due to visit the UK towards the end of this week. “I’d love to have Trump come watch me,” he said. “That would be awesome. Maybe I’ll tweet at him if I win on Wednesday. I know a lot of people won’t like that, but I don’t care.”

Fellow American Serena Williams wasn’t as enthusiastic when asked for her thoughts on Trump watching her in Saturday’s women’s final, if she gets that far. “I feel like he has the right to do whatever he wants to do,” she said. “If he wants to come to a Wimbledon final, he has that right.”

“I hope I’ll be there,” Williams added. “I still have a lot of matches to win. For me, I can’t even think that far.”

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