Diego Maradona criticised Jorge Sampaoli and says things must improve if the Argentina coach wants to keep his job.
Argentina were held to a surprising 1-1 draw by debutants Iceland in their first group game of the World Cup, with Lionel Messi missing a penalty during the second half.
Maradona, who has previously led the national team, was scathing in his comments on former Chile and Sevilla head coach Sampaoli.
"If he carries on like this, Sampaoli can't come back to Argentina," he said, while working as a pundit on Venezuelan and Italian television.
"His game plan was a disgrace. Even though the Iceland players average 1.90m in height, we played all our corners into the air. We had no short game.
"I don't blame the players. I blame a lack of preparation because there obviously hasn't been any.
"You can bring 25 brilliant players with you, but you have to work with them. We can see that Iceland was better drilled than Argentina and that is a massive shame."
Maradona was also surprised that Argentina could not get the basics right and admits he has concerns on the reliance of Messi heading into their second fixture against Croatia.
"It was extraordinary to see Argentina without any answers, keeping their heads down, struggling to play accurate passes or one-twos," he added.
"Messi was their only outlet. There is serious trouble ahead because Nigeria has experience, they know how to counter-attack and they know how to score."
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