Juan Martin del Potro sets up clash of the giants against John Isner as men’s US Open draw begins to swell

Isner defeated Milos Raonic in five sets on Sunday to continue the march of the big-hitters at Flushing Meadows

Just like at Wimbledon earlier in the summer, the latter stages of the US Open are being peppered with some heavyweight confrontations in the men's singles. John Isner won the latest of them with his 3-6, 6-3, 6-4, 3-6, 6-2 victory here on Sunday over Milos Raonic and on Tuesday the American’s quarter-final meeting with Juan Martin del Potro will be another battle of the giants.

Del Potro, the 2009 champion here, reached the last eight of his favourite tournament by beating Borna Coric 6-4, 6-3, 6-1 to maintain his record of not having dropped a set in this year’s event.

The 6ft 6in Argentinian may well start as the favourite against the 6ft 10in American, but 33-year-old Isner has played some of the best tennis of his career this year, having made a major breakthrough when he won his first Masters Series title at the Miami Open in the spring.

“I feel very tough mentally,” Isner said. “I think I really turned a corner in Miami this year. There are some matches I've played where I still rely on my serve, but I think more times than not this year I've shown some other ability. That comes from just being relaxed on the court. It's not a product of more reps and more practice.

“The mental part of the game, being able to free up on the tennis court, is much easier said than done. For the most part I've been able to do a pretty good job of that this year. In the past, that's what's held me back.”

Isner thinks he is a better player than when he last reached the quarter-finals here seven years ago. “Physically I'm stronger, I’m wiser and I have a lot of experience on my side,” he said. “I'm feeling really good. I’m just in a good place, happy. I'm really enjoying competing, not putting too much pressure on myself. To do that at 33 now is pretty cool.”

Isner, who hit 56 winners, including 20 aces, in his victory over Raonic, thinks the experience of losing his record-breaking Wimbledon semi-final to Kevin Anderson this summer has helped him in the long term. The world No 11 won the 14th title of his career in Atlanta in his first tournament after Wimbledon and has been in fine form here.

Juan Martin del Potro is through to the US Open quarter-finals after beating Borna Coric (Getty)

“After Wimbledon, that was very tough,” Isner said, recalling his five-set defeat by Anderson, which at six hours and 36 minutes was the second longest match in All England Club history, beaten only by the American’s 11-hour marathon against Nicolas Mahut in 2010.

“I was beat up mentally and physically from that match. But it was also a very good result for me. Even though it was tough to lose that match in the fashion that I did, it was still a very encouraging result. I took a lot of positives from that tournament. I think I carried that on into this summer.”

Del Potro beat Borna Coric to maintain his run of not dropping a set (AP)

Isner said the support of the crowd in Louis Armstrong Stadium had been a big factor in his victory over Raonic.

“It helps so much,” Isner said. “Adrenaline plays a huge part in tennis, especially at a tournament like this for an American like myself. My relationship has always been amazing with this tournament. The fans are incredible. I'd love to have them on my side in the next one.”

John Isner celebrates after beating Milos Raonic (Getty)

Isner has lost seven of his previous 11 meetings with Del Potro but insisted: “It’s a match-up that I enjoy. He's one of the best players in the world. You’ve got to step up your game against a player like that.”

Del Potro always looked in control against Coric, who had lengthy treatment for a problem with his right leg in the second set.

Milos Raonic suffered defeat against Isner in five sets (AP)

“I love to play with this energy from the crowd, from the people,” Del Potro said afterwards. “They make me feel special to play my best tennis every year.”