"Time machines don't exist," snapped Okada, who has come under intense pressure since hosts Japan finished third in last month's East Asian championship.
"We know we have problems to work out," added the coach, whose team have been booed off the pitch in their last few games.
"But what's done is done. There's no point dwelling on the past," he told a news conference on Tuesday.
Okada is set to push CSKA Moscow midfielder Keisuke Honda into a forward role to generate extra firepower for Wednesday's game.
"The good thing about him is his ability to create goalscoring situations and his physical strength," said Okada.
"He can probably be more lively through the middle."
Honda himself gave a blunt assessment of Japan's recent struggles in front of goal.
"It's too late to be debating the lack of shots we take," said the 23-year-old. "It should have been addressed much quicker and the players are aware of the problem.
"I'm not the saviour or Cristiano Ronaldo. We need to play with a sense of urgency and there will be no room for excuses for not scoring goals against Bahrain."
Honda added: "It's a World Cup year and we need to stay positive."
Japan and Bahrain have already booked their spots at next year's Asian Cup in Qatar but anything less than victory for Okada's side would be a severe blow.
Playmaker Shunsuke Nakamura insisted, however, that Japan should be bold enough to take a few risks.
"We should use the game as an opportunity to experiment," said the 31-year-old, who has just returned to Yokohama F-Marinos from Spain's Espanyol. "We can afford to make mistakes."
