Marchetti has been frozen out at Cagliari this season due to a contract dispute.
"How much do I miss football? So very much," he told the Gazzetta dello Sport after playing for the Primavera youth team this weekend.
"I like to play, challenge myself and take on every obstacle. Many ask me how it feels to go from representing Italy to being locked out of the sport.
"My answer is that I left home at 14 for football, so anything is possible. The important thing is not to give in.
"With a professional attitude, sacrifices and values, the truth always comes out."