Even though Browns quarterback Jeff Garcia may be ready to play, the Browns like what they saw from rookie quarterback Luke McCown when he faced the Patriots last week. They may be grooming him for the starting quarterback position as well - whenever that may be.
If Luke doesn't play well against the Bills, it's unknown if Garcia would take over the next week or not. Even if Luke does play well, the Browns may let Garcia play if they plan to have him as the starter for next season.