Australia’s Alex de Minaur has secured a spot in the Washington Citi Open quarter-finals after winning twice on the same day.

The 19-year-old defeated South Korean eighth seed Hyeon Chung 6-2 4-6 6-2 in a match lasting close to two hours.

Earlier de Minaur overpowered American Steve Johnson 6-4 7-5 .

Fellow Australian James Duckworth was bundled out after falling in straight sets to Stefanos Tsitsipas.

The world No.654 went down to the 10th-seeded Greek 6-3 6-4 in just over an hour.

German brothers Alexander and Mischa Zverev faced each other in at ATP main-draw match for the first time, with No.1 seed and defending champion Alexander winning 6-3 7-5.

Alexander advances to the quarter-finals where he’ll face Japan’s Kei Nishikori.

The brothers had met twice before in qualifying matches, most recently in 2014.

Their match ended with a lengthy embrace with Mischa saying despite the loss it was a contest he would always remember.

“After the coin toss I had tears in my eyes because it felt so special,” he said.

“I wondered what are my parents thinking right now. I needed a few seconds to bite my tongue and focus.”

The brothers’ moment as adversaries didn’t last long .

They headed to a different court and backed up for a 6-1 6-4 win over Oliver Marach and Mate Pavic.

In other action in the US capital, Wimbledon semi-finalist John Isner was beaten by the lower-ranked Noah Rubin.

A weary-looking Isner was broken twice in the opening set to lose 6-4 7-6 (8-6) to Rubin, ranked 152nd in the world.

Isner was coming off a title in Atlanta last week while Rubin will now meet Russian Andrey Rublev in the next round.