Japan, bidding to reach their first ever quarter-final and carry the hopes of Asia, barely had a clearcut effort at goal in one of the worst matches of the tournament so far with Paraguay little better.
"I don't think I have anything left to do now, probably," Okada told a news conference when asked if he would now be leaving, although he said a definite decision would take time.
"It's my responsibility, we did not insist enough. I can not elaborate any further. When I look back at what I could have done for the players and what I did as a head coach I should have been more insistent on winning."
"All substitutions and changes I made were to try to push," said Okada, who boldly targeted a semi-final spot prior to the tournament but almost ended his second spell in charge after defeat in a World Cup warm-up against South Korea.
"It's difficult to narrow down why we couldn't score. We are not a team that can score lots of goals."
