It would have been made obvious to him that he would not be a first team regular, especially since Milan were in negotiations to sign Rivaldo at the time, but he now appears to be unhappy at the situation.
And Atalanta, Dalla Bona's first club, look set to re-sign him on loan before making the deal permanent. Whilst the negotiations are still in their early stages, reports in Italy suggest that the deal should go through... but this is the same newspaper that said the Dino Baggio deal was a dead cert, so Chelsea Mad are taking these Dalla Bona rumours with a pinch of salt.
Along with Rivaldo, Milan boast the likes of Rui Costa, Andrea Pirlo, Rino Gattuso, Serginho, Clarence Seedorf and Redondo in midfield, so it was laways going to be tough for Sam to establish himself at the San Siro.
At this moment in time, I'm willing to bet that Sam is regretting his move from Chelsea, as he would have been certain to be a first team regular this season. But money talks...