Gallo is basically in his rookie year on a team that is in massive flux. His lack of aggression may relate to timidity, but it also must come from the radical changes on the team. Adding a guy like TMac mixes things up quite a bit. Gallo will be fine. And I disagree about his potential: I think he could most definitely become as good or better than Dirk. Similar size, similar games. For me, Gallo is untouchable. I am glad MDA is lighting a fire under his arse. It will help him and it will solidfy their relationship.
That said, I love Chandler, too. He is a defensive stopper, and a finisher. But he is not exactly a "complete" player. I would like to see him develop better court vision, get a few assists, and develop a reliable pull up jumper. Don't need him chucking three's, but a higher percentage behind the FT line would be nice. Like to have him draw more fouls and get fewer charges. I would certainly try to keep him, but he is the best trading asset if we find an upgrade (e.g., Rubio) or get lucky with a 2/3 in the draft.