I think Casilla will be ok. I don't think I would count on too much improvement. Cano should rebound some and he will fall further in the draft so he may have good value. Weeks will be on my watch list only . He killed me last year. Lopez seems a better bet to be solid again.
The way I see 2nd base , is that if you don't get one of the top 7 ( Utley,Pedroia, Kinsler, Phillips, Roberts, Uggla, and Ramirez ) then you may as well wait until the late rounds to get value from that position. Between Lopez, Cano, DeRosa, Polanco, Kelly Johnson, Iwamura,Casilla, Kendrick, or Ian Stewart , one or more of these will be available real late in the draft. No need to hurry. There's also Hudson and Hill that may be ok also.
Dan the Bluesman