The Bayern Munich man returns from suspension for his side's all or nothing clash with Cameroon in Manaus on Wednesday.
The Bayern Munich forward missed his country's defeat to Brazil in their Group A opener last Thursday after being sent off in the second leg of its qualification playoff victory over Iceland.
However, he has now served his ban, meaning coach Niko Kovac will be able to unleash him in Croatia's crucial clash with Cameroon, who were beaten 1-0 by Mexico in their first game.
And Pranjic, who also missed out against Brazil because of injury, believes his team will be better off with Mandzukic leading the line.
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"Mandzukic definitely makes us stronger and you can't replace him like-for-like," the 32-year-old told FIFA.com. "He's prepared to go out and die for the cause. Nikica Jelavic did really well against Brazil but Mario is Mario. We need him. We're a totally different team without him."
Kovac’s side will be desperate to get off the mark following their 3-1 defeat against, suffered in controversial fashion with complaints that a number of key refereeing decisions went against them, and Pranjic warned his team-mates that it’s now win or bust.
“It's all-or-nothing for both teams,” he said. “The losers will pack their bags and go home. We have to be ready for everything and play like it was our last match.”