i'm a little confused by the question, actually. are you advocating that we pull him no matter what at some point in the first 4 games, or are you asking how many bad games it takes before he gets pulled?
If its the bad games, I say 2 1/2. He and Smith were basically close this offseason so I really don't think the coaching staff will hesitate much before making a switch, but you got to give him 2 games at least to see if he can pull himself out of it. If by halftime of the third game he's playing like crap, then you make the switch.