he's a 5th round pick, it's a little harder for someone picked that low to get chances, especially when he didn't even look that good in preseason. It's not just, try any QB, there has to be something there and he has to show something in practice.
The playoff race is not the time to throw stuff at the wall and see if it sticks, tried it once and a miserable failure. If he starts against Miami and has another horrible game, you fire the coach.
Wait til next season, you'll get your QB change.