edit: not sure why this posted twice. just ignore this one.
Sheridan was put in because Threet was limping.
In addition, if something were to happen to Threet, I would be happier knowing that Sheridan has at least played in some garbage time throughout the year.
Sure, not all of them went to the guys with the right uniforms, but nobody's perfect. 3 of 5 with 2 interceptions.
Like scottiemmm said, Threet looked hurt, and frankly at that point the game was out of reach anyway--especially in that weather.
Where's Charlie Bauman when you need him?