http://www.chicagonow.com/cubs-den/2015/07/trade-rumor-thread-deadline-moving/
I've also heard that if the Cubs were to deal Starlin Castro, the most likely suitor is the San Diego Padres, who are always looking for offense and a return to form would give them surplus offense at a premium position. As I have mentioned, though, there is risk with that and my guess is that if the Padres are to take on Castro, it would only be in some sort of deal for James Shields and a big portion of his remaining salary.
UPDATE: 7:10 PM: Per David Kaplan, the Cubs are chasing Cole Hamels but David Price is not in play. At least not yet. Here is the money quote on Price...
Several reports have indicated that the Cubs have been in discussions with Tigers GM Dave Dombrowski regarding Price's availability but those do not appear to be accurate at this point. Cubs sources insist they have had no substantive discussions regarding him yet.
I am sure that won't slow down the speculation, but there is a lot of public information coinciding with the things I have heard privately.
Interesting though. Castro for Shields. I think that deal would go strait. Maybe a toss in from each side if anything. It would fix 2 problems for the Cubs. A controlable SP and it opes up a MI spot for Baez. I like it.