Trapattoni has been criticised for the team's performance at Euro 2012, but assistant manager Tardelli has stated his bemusement as to why there have been calls for Trapattoni to be replaced.
Tardelli said: "Giovanni wants to work always every day. He is full of enthusiasm, just like he was the first time I met him.
"I don't understand why Giovanni is being criticised because he achieved good results."
Republic of Ireland begin their World Cup qualifying campaign against Kazakhstan on Friday.