Japan's Keisuke Honda has warned the Asian Cup holders not to take their foot off the gas following Monday's 4-0 thrashing of Palestine in their tournament opener.

The Blue Samurai were never threatened in their Group D game but after blowing out the cobwebs in a light training session on Tuesday, their midfield dynamo cautioned against overconfidence.

"Football rarely goes exactly to plan," he told reporters before Japan moved to Brisbane for their next game against 2007 title winners Iraq. "After you have a big win, you often have a bit of a letdown so we have to be prepared for that."

Honda's advice will carry extra weight following the team's meek exit from last year's World Cup after which the Japanese cult hero burst into tears, blasting himself and his team mates as "pathetic."

As at the World Cup, Honda was on target in Japan's opening game, scoring from the penalty spot, but the AC Milan player trained separately from the rest of the squad for part of Tuesday's session.

"I just took the decision that it would be better for me," he said, brushing off any injury concerns. "We controlled yesterday's game, but it's gone now and we have to look forwards and approach the next one in the same vein. That will be the key."

Japan coach Javier Aguirre looked less than amused as his players appeared to lose concentration after scoring three goals in the first half to kill the game.

After capturing a record fourth Asian Cup four years ago under Alberto Zaccheroni, the Mexican has little margin for error, and will be feeling the pressure with title rivals Australia and Iran looking sharp in their opening games.

"If we keep battling and go about things the right way the results will follow," insisted Honda. "We just need to focus on taking three points (against Iraq)."

Japan round out their first-round matches against Jordan in Melbourne on January 20.