Reilly Opelka has beaten fellow American giant John Isner to win the US Men’s Clay Court Championship title, claiming the tallest ATP Tour final in the Open Era.

Opelka, 24, triumphed 6-3 7-6 (9-7) in one hour and 50 minutes against his 36-year-old opponent to secure his first ATP title on clay.

The final at the River Oaks Country Club between the 211cm Opelka and the 208cm Isner was the tallest on the ATP tour in the open era.

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Opelka clinched the only break of the match in the first set and went on to save three set points in the second-set tie-break, fighting back from 6-4 down to win his fourth ATP tour title.

“He was my idol growing up as a kid, and before I even met him, I liked him. But since we’ve become such good friend and spent so much time on Tour, I like him even more now,” 24-year-old Opelka said of 36-year-old Isner during the trophy ceremony.

“He’s been an unbelievable role model for not just myself, (but) Taylor Fritz, Frances Tiafoe and Tommy Paul.

“We all say the same. He’s been an unbelievable competitor for a long time.”

Opelka and Isner often joke with one another that they are “Servebots” — or “Bots” for short — who are only known for their serving.

But there were 13 break point chances and five mini-breaks in the second-set tie-break, with the clash coming down to returns and passing shots in the critical moments.

“We’ve played a handful of times and you keep on beating me. I hate you for that!” Isner, the 2013 champion in Houston, joked.

“But it was really cool to play you in a final. I think that’s very unique.

“Obviously there are a lot of similarities between Reilly and I, but I’m much older than him and he has a lot more years ahead of him on Tour, so for me to get to play you in a final, I think that’s very, very special.”