The Asian champions were missing their usual pace when moving the ball up the wings and lacked ideas near goal during the Group C match, he added. (Agencies)
"In the second half we had more people out there and we should have circulated the ball more quickly," said the Italian. "We played way too slowly. There wasn't much movement and there wasn't much depth,” he said.
"The space between us was extremely tight and that posed a problem. We should have had more speed in making our passes and receiving our passes," he added.
A desperate rearguard action from Greece kept Japan at bay despite the dismissal of their skipper Kostas Katsouranis for two yellow card offences after 38 minutes.
The Japanese, who like Greece have one point from two games, dominated possession but were unable to convert their chances and rarely troubled the opposing keeper. They need to beat Colombia on Tuesday to have any chance of advancing.
Zaccheroni said his players lacked creativity with the final ball but he urged them to stick to the intricate, quick-passing game that made them the first nation to qualify for the finals.
"Japan should be brave enough to play at the international level by imposing its game on opponents and playing fast," he said.
"In the last two games unfortunately we were not able to play with the speed we were accustomed to," he said.
The Asian champions were missing their usual pace when moving the ball up the wings and lacked ideas near goal during the Group C match, he added.