Several years ago I had the opportunity to talk to Jeff Pentland, the former Cubs hitting coach. He had been lauded for helping to change some of the Cubs approaches at the plate, getting them to work the count more, etc. Yet just a short time later he was gone, fired. I asked him what the difference had been, and he simply said that the players just stopped listening. He said that they still tried the approaches he recommended, but they just didn't execute as well.
The Cubs can't fire 25 players, but they still need a shock to the system. They need a new approach at the plate, a refined focus and a different attitude. And, unfortunately, the best shock to the system is to let Gerald Perry go and bring Von Joshua up. Joshua already has a working relationship with several players - like Theriot - which leads me to believe that Perry has lost some credibility with the team. At a minimum, the guilt felt by the players at the demise of a trusted coach might be enough to shake things up.
Just my two cents.