Friday's FIFA World Cup draw pitted the reigning champions in Group B, along with 2010's beaten finalists Netherlands, Chile, and Australia.
It is the first time that the two finalists from the previous edition of the tournament have been drawn together in the group phase.
And Mendieta, who made 40 appearances for Spain between 1999 and 2002, is taking nothing for granted.
"I don't think it's an easy group at all," he said.
"Chile have more to their squad than people might realise, and Holland are technically and physically very strong, so Spain know they will have to be on their toes."
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