Tunisia lacked final touch to score against Australia, says coach Jalel Kadri
Mitchell Duke's goal in the 23rd minute was enough for Australia to win a World Cup match for the first time since 2010.
Tunisia will now need to beat defending champions France in their last group-stage match to have any chance of progressing.
"We lacked the final touch and weren't realistic. The performance in the first half was not up to expectations and we did not create many chances," Kadri told reporters.
"The situation changed in the second half and we created several chances, but we failed to put the ball in."
"Australia forced us to play with their style and we were more reacting rather than acting, and Australia relied on physical strength. So we can't say that we produced a bad performance overall but we lacked effectiveness in front of goal."
Kadri said he felt his team did not deserve to lose but failed to take their chances while Australia scored with only two shots on goal.
"We lost a crucial match, but we will give everything we have in the last match," he said, adding that he will make several changes in the last match against France.
"We don't change the squad for the sake of changes, but we make adjustments to adapt to the way the rival teams play. We will analyze our performance and fix our mistakes."
France, who beat Australia in their match, will qualify for the last 16 if they beat Denmark later on Saturday.