I guaran-damn-tee you if Trubisky comes into the game at this point the prevailing mentality would be "hell f-ing yes lets do this". These guys are alpha males, they are driven to succeed, they want to play well, they are looking for any excuse whatsoever to get fired up. You give them a new QB, one that's clearly the future of the franchise on the field, and they are going to go all out. It doesn't matter if they can win that game, they are seeing their future unfold. Anyone that's ever been in a remotely similar situation can relate. It's a glimmer of hope where there was none. You know Glennon's not the savior, but this guy might be? I'm pretty sure there are about a dozen movies that start out just like this. Those players would kill to be part of that narrative.
While I doubt the veracity of a source, I think it's pretty clear he's just going through the motions and would be content to get fired so he gets paid out.