The defeat in Bloemfontein on Monday against the supposed group whipping boys leaves Cameroon facing possible early elimination with matches to come against Denmark and the Netherlands.
"We lost a golden opportunity. It was like throwing away a joker in a game of cards," he told Reuters on Wednesday.
"The only thing left for us now is reviving our fighting spirit and working hard, seriously, to win the next game."
The 36-year-old goalkeeper was one of several surprise selections and positional changes made by coach Paul Le Guen on the opening day of Group E.
He replaced long-time stalwart Carlos Kameni in the starting lineup, which included midfielder Alexandre Song and saw captain Samuel Eto'o play as a right wing.
Midfielder Enoh Eyong, the other player who spoke to reporters after training in Durban on Wednesday, said Cameroon had to beat the Danes in Pretoria on Saturday or otherwise face up to an early trip home.
"There is only one way out for us: victory. We have to put more firepower in the next game. It is like a final for us because if we don't get the best of it, we're finished," he said.
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