I think both Pato and Boateng are desperate cases, the duck is always injured for how many, 2 or 3 years now? Boateng retired from NT at the age of 24 or 25 to stay healthy and still had plenty of injury problems last year. Diarra would fit Milan well, he's also has had his fair share of fitness problems in past, watch Milan sign him and later moan about being unlucky with injuries.
Montolivo is Aquilani's twin sister, but if Milan has fit Cassano and Ibra upfront available all season, that alone makes them huge contenders.