Washington, DC, USA, 3 August 2018 | AAP/tennis.com.au

Australia’s Alex de Minaur has reached the quarterfinals of the Citi Open after winning two singles matches on Thursday in rain-soaked Washington DC.

The young Aussie defeated No.8 seed Hyeon Chung 6-2 4-6 6-2 to set up a possible meeting in the last eight with Andy Murray.

Murray is currently a set down to Romania’s Marius Copil, the world No.93.

Chung, at No.23, is the highest-ranked player De Minaur has beaten in 2018 and the result sends him through to his first quarter-final at ATP 500 level.

De Minaur led 6-2 3-1 before his Korean opponent – an Australian Open semifinalist earlier this year yet making his way back after a two-and-a-half month injury absence – fought back.

But in the third, De Minaur’s fighting spirit and match toughness proved decisive. He retrieved relentlessly and opened up a 5-1 third-set lead over his more powerful opponent before wrapping up victory in just under two hours.

Earlier, De Minaur reached the third round with a 6-4 7-5 defeat of Steve Johnson.

The 19-year-old world No.72 hit five aces to overcome his American opponent in a match lasting an hour and 40 minutes.

De Minaur led the 11th seed 5-4 in the opening set on Wednesday before play was suspended due to rain.

When the match resumed, De Minaur continued to fire and notched his second win over Johnson this year, having also beaten him at the Brisbane International in January.

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

The world No.654 – who entered the even using a protected ranking – went down to the 10th seeded Greek 6-3 6-4 in just over an hour.

Despite the loss it was a good week for Duckworth, who scored his first two wins at tour level since Tokyo in October 2016.

He’s projected to jump more than 200 places to around No.440 when the new ATP rankings are released on Monday.