Big-serving Ben Shelton blew away fellow American Tommy Paul to reach the quarter-finals of the US Open.

The 20-year-old from Atlanta fired down two 149mph serves in one game on his way to a 6-4 6-3 4-6 6-4 victory at Flushing Meadows.

“I think it was straight adrenaline,” he said. “In any other atmosphere I don’t think I could get it done. I think my arm would fall off, but it’s feeling good right now.”

The record fastest serve at the US Open is still held by Andy Roddick, who hit a 152mph thunderbolt on his way to the title in 2003 – the last time an American man won their home slam.

It was sweet revenge for Shelton, who was knocked out by Paul at the same stage of the Australian Open in January.

He added: “I really learned how to be mentally tough. When I was playing in Australia after a long week, I was looking at my box saying ‘my legs are dead, I’m tired, I can’t go anymore’.

“I realised how important it is to believe in myself, believe that I can go all the way, the full distance emotionally and physically and now I have that belief here.”

Shelton will play 10th seed Frances Tiafoe, guaranteeing an American man in the semi-finals.

Tiafoe beat Australian wild card Rinky Hijikata in straight sets, 6-4 6-1 6-4.