Colback has no chance of going to Brazil so he has slightly different priorities, I don't think he'll be dropped however. Then again, Giacc too has no chance of playing for Italy if he cant keep his place in a relegated threatened team. I'm sure that's how Prandelli and Giacc himself are looking at it. That said I can understand if he wasn't used due to the physical nature of Derby's. I just hope he's back soon as he is our most creative player by a country mile.
He was dropped from the italy squad around the time he signed, since he's showed good form and got back in. The move has done him no harm so far. Don't panic fella he's an important player.