I call false that his numbers slid. Let's do a comparison of his numbers from 2012 to 2013 through the first five games of each Season to see if his numbers "slid quite a bit" or at all:

2012 Passing: 106/145 73% Comp, Passing for 1,283 Yards 12 TD and 4 INT
2013 Passing: 132/186 71 % Comp, Passing for 1,362 Yards 17 TD and 1 INT
Conclusion: He passed for more yards, more TDs and fewer INT through five games in 2013 than 2012

2012 Rushing: 57 Rush for 206 yards 3.6 yards a carry 0 TD
2013 Rushing: 52 Rush for 224 yards 4.3 yards a carry 2 TD
Conclusion: More yards, more TDS and more YPC in 2013 than 2012

Overall conclusion: Keeton was getting better in 2013 and the numbers showed it. They did not slide at all, but improved in almost every conceivable metric. I don't think 19 TDs through the first five games are "game manager" like numbers at all. I get that BYU fans don't think he's very good because BYU has owned Chuckie. Bronco has learned how to contain him. I hope that changes this year, but won't believe it till I see it. Ask Utah fans if they think Chuckie is a good QB. The fact that he hasn't played well against BYU doesn't mean he's not a stellar QB- which I believe him to be.