Belleri started his career at Lumezzane. He played in Serie A for Empoli in the 2002–03 season. When Empoli failed to protect his place in 2004, Belleri, Di Natale and Cribari were sold to Udinese in a co-ownership deal, with Almirón and Nomvethe moving in the opposite direction. Emílson and Belleri were sold to S.S. Lazio the next year. Belleri signed a 4-year contract in another co-ownership deal for €250,000. In June 2006, Belleri, Cribari, Goran Pandev and Stefano Mauri were acquired outright from Udinese for €400,000, €3 million, €4 million and €3 million respectively.