I can see Bill wanting to get a good eval on both guys, but wanting to protect Mac from having to answer questions from the media about losing his job, so he waited on announcing anything. If he told the team there may have been leaks. Now he can switch to Zappe for the game and assuming Zappe is even a little better, Zappe will be the new starter going forward and can take over as the guy doing the press conferences and Mac won’t have to deal with all of that. Conversely it also keeps the pressure off of Zappe this week and lets him just prep relatively quietly without the media breathing down his neck.