Australia captain Tim Cahill is looking to remain positive despite suffering a 1-0 defeat to South Korea in their Asian Cup match.

The Socceroos forward is urging his teammates to look forward to their knockout game with China in the quarter-final stage of the competition.

The hosts lost their first match of the tournament on Saturday as Lee Jung-Hyub scored a first-half winner to see South Korea top Group A and leave Australia a difficult path to reach the final.

"We now have to get up and go again. We've got China in five days and, the way I see it, we did not take our chances tonight and, if we had taken one of them, we would have been on our way to Melbourne [to face Saudi Arabia or Uzbekistan]," the 35-year-old told reporters.

"That was not to be but we still have a lot left in the tournament and tonight it would have been good to get that result.

"If we got the draw we deserved it would have been fine. Korea are a good football team and played really well, they crowded their third of the pitch and were physical."

Australia coach Ange Postecoglu used Cahill as a substitute in the game, with the skipper coming on with 20 minutes left to try to salvage a point.