Tebow is simply not a QB period. You can go out on a limb and say he's better than many backups I suppose. I can give you that but they suck as well. Difference is Tebows skill set and style are so unique and not made for Nfl really you have to completely change your offensive schemes and playcalling to accommodate him. Just more headache than he's worth for a backup I suppose is most coaches reasoning aside from lack of ability throwing/reading defenses.