Unseeded Aussie tennis player John Millman has claimed the biggest scalp of his career, defeating world number two Roger Federer in four sets at the US Tennis Open.

He’s the first Australian man to reach the quarter-finals at the US Open since Lleyton Hewitt did it in 2006.

Millman, who’s ranked 55th in the world, won the contest 3-6 7-5 7-6 7-6.

Craig Gabriel spoke with Chris Smith just moments before Millman secured the victory, giving a step-by-step account of the final tie-breaker.

Click PLAY below to hear Craig Gabriel call the victory

29-year-old Millman will play Novak Djokovic on Thursday.

It’s the first time Federer has lost to a player ranked outside the top 50 at the US Open.