Translation:The famous referee made a big mistake.
"Error" is now accepted. Thank you for your input ^.^ But keep in mind:
Error is a direct translation to σφάλμα, not λάθος.
Error and mistake are not always interchangeable. They are synonymous, but generally, a mistake is a choice that turns out to be wrong, while an error is a bit more of a formal and technical term (just like σφάλμα is in Greek), referring to something that's wrong due to some lack of knowdedge or rule/protocol violation.
In this case, of course, it's correct, because in sports, rule violations are called 'errors', so the coach could have made a regrettable decision, or violated a rule. ^.^