The 31-year-old had a reputation for ill-discipline off the field during his younger days but was widely lauded for exhibiting a more mature attitude last season, which played a part in Cesare Prandelli recalling the forward to the Azzurri squad for this summer's trip to Brazil after two years in the international wilderness.
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"Cassano is one who is out of his mind," he told Sport Mediaset. "One day he fought with the woman that was cleaning his room. He raised his voice. He shouted in her face. He's wild!"
Guaragna also claimed that Cassano and fellow forward Mario Balotelli were isolated from the rest of the Italy squad.
"I saw Balotelli detached from the team, and also Cassano," the hotel manager explained.
"[The rest] were very nice with us, especially [captain Gianluigi] Buffon. He was very calm, the most concentrated.
"It's a shame because they had all the tranquillity in the world here, but to win one needs a united group. Italy were a divided squad.
"Everyone's feeling is that they lacked the spirit that must accompany preparations for a World Cup."
Italy were eliminated at the group stage, after following up a 2-1 win over England with successive 1-0 losses to Costa Rica and Uruguay.