Del Piero is a big fan of the Spanish boss.
Speaking to Marca, he said: "He is a genius. What he built at Barcelona, winning six titles in a year, is unique.
"Not just because of the victories, but also because of the way in which they played.
"They dominated play in each match and it was very nice to see them play. He's trying to replicate that in other countries."
Del Piero admits that with Guardiola in charge, City have more than a chance in the Champions League.
"He broke a number of records last year with great football."