Marchetti has revealed that he held out hope of joining Sampdoria this summer.
He said: "I went through the end of the season and training camp with Italy hoping for an opportunity at Samp.
"It's normal to be ambitious. I thought about improving myself, having a new challenge, and growing on an international stage in the Champions League.
"There is regret of that there isn't any doubt. But I cost too much and I stayed at Cagliari. I owe this club a lot."