Coach Roger Lemerre was bitterly disappointed as Tunisia were held to a draw, despite Radhi Jaidi salvaging a point for his side with a late header.
Heading to a draw - Tunisia (white shirts) and Saudi Arabia battle it out in the 2-2 thriller in Munich
"We weren't very assured. While the first goal gave us a boost, it was not enough," said the former France boss.
Midfielder Adel Chedli added: "What didn't work for us? Everything. It was a catastrophe. We never really found our rhythm.
"We led 1-0 at half-time but then did some foolish things."
Tunisia became the first African nation to pick up a point in Germany but Chedli took little consolation from that.
"I didn't recognise our team in this match but on Monday we hope to be a different team aginst Spain," he said.
"We definitely aim to still qualify and if it means we have to beat Ukraine in the last match then we will do everything to beat them."
Despite the result, Tunisia captain Riadh Bouazizi insisted that the most important thing was not to lose the match as it kept Tunisia's qualification hopes alive.
"We could have won, yes, but when you look at it we got a point, Ukraine have none and we are still competing to qualify," Bouazizi said.
Goalkeeper Ali Boumnijel, who became the fifth oldest player to compete in a World Cup at the age of 40 years and 62 days, added: "We have to keep calm now.
"Will recover, watch our mistakes and not make them again against Spain in our next match."