Stanislas Wawrinka has admitted that he does not know much about second-round US Open opponent Chung Hyeon.
The world number 69 beat Australia's James Duckworth in straight sets in the opening round at Flushing Meadows to set up the meeting with the fifth seed.
The French Open champion told reporters: "I don't know him. Honestly, I saw him playing. I saw the score. I saw him playing good match, beating some good player. He beat my friend [Benoit] Paire last week for example. So I know his result.
"I know his ranking, what he did this year. Never had a chance to see him play live or on TV. My coach did a few times this year, so I'm going to talk to him."
Chung qualified for the US Open for the first time this year, and made his Grand Slam debut at Wimbledon in June, losing in the first round to Pierre-Hugues Herbert.
