De Bruyne's move from Manchester City to Napoli was confirmed on Thursday.
Stramaccioni told Il Mattino: "Did I expect the Belgian to play in Serie A? Honestly, no: if we take into account the flexor injury that kept him out for two months in October, he has practically always played as a starter in both the Premier League and the Champions League.
"A protagonist in all of City's big matches this season and only remaining on the bench in the return match in Madrid. It's an extraordinary move. Because in addition to the player's value still being at the highest level, you're going to get a man who will have great ease in adapting thanks to his true friendship with (Romelu) Lukaku and all the advice and guidance on Napoli and Napoli received from Dries Mertens, another great friend of his.
"His adaptation will be much easier than normal."
Stramaccioni added: "He may not have the devastating physical features he had a few years ago, but he is an iron professional, a hard worker who lives a serious life and takes care of his body. He is 33, he is whole and mature. Perfect for Serie A."