JOHN MILLMAN WAS stunned after his shock win over his “hero” Roger Federer at the US Open.

The Australian caused a huge upset at Arthur Ashe Stadium, beating an uncharacteristically poor Federer 3-6 7-5 7-6 (9-7) 7-6 (7-3).

Millman, whose victory was his first over a top-10 player, was left amazed by his triumph as he paid tribute to Federer.

“I’m probably in a little bit of disbelief,” he said during an on-court interview.

“I have so much respect for Roger and everything he’s done for the game and he’s been a hero of mine. Today he was definitely not at his best, but I’ll take it.”

Federer endured massive struggles with his serve throughout the fourth-round clash, the second seed finishing the encounter with a first-serve percentage of 49.

Millman – who faces Novak Djokovic in the quarter-finals – acknowledged the Swiss great’s off day, but said he grew into the meeting.

“I felt like a bit of a deer in headlights to begin with, to be honest with you, the feet weren’t moving. Roger had it on a string, he was manipulating me around the court,” said Millman.

“But I got out of a tough second set and really found my feet and started to be a little bit more aggressive.

“I think I started to serve really well and probably capitalised a little bit on Roger having an off service day.”