I think this is a very important question. In my opinion, 3b is deep. Really deep. Blalock, A-Rod, Rolen, Lowell, Ramirez, Chavez, Tex, Huff, Mora, the list goes on. D. Wright will soon be there.
I drafted A-Rod first overall in my dynasty keeper league, and I'm starting to think he might not be a top 5 pick next year. It depends on how strong his second half is, and if he keeps stealing. If he does, an argument certainly can be made that he should be the first overall.
I've considered dealing him this year, but I have been hesitant because he certainly can be the best fantasy player around when he is locked in. I'm not sure where his value lies for the future, but if you can get him for Manny, I'd do it in a heartbeat. He is capable of matching Manny's stats this year with an additional 25 SB's.