First off, a rookie season is very, very rarely indicative of a whole career's worth of performance. Let's just get that out of the way.
Secondly, Mike Glennon was hardly given any chance to succeed given his circumstances. Think about it. He was thrown into a bad coaching situation, with a regressing O-Line, and running backs who might as well have been walking backs. That's a level of pressure many starters in the NFL today could not handle, let alone a rookie.
I hear someone yelling drunkenly "STATS!" So I will give you stats. Let's compare Mike Glennon's rookie season to Nick Fole's:
Nick Foles 2012: 7 GP, 161 CMP, 265 ATT, 60.8% CMP%, 1699 YDS, 6.41 AVG, 6 TD, 5 INT, 43.1 QBR, 79.1 PRAT.
Mike Glennon 2013: 13 GP, 247 CMP, 516 ATT, 59.4 CMP%, 2608 YDS, 6.27 AVG, 19 TD, 9 INT, 45.6 QBR, 83.9 PRAT.
For every stat that isn't an average or percentage, Nick Foles and Mike Glennon had nearly identical rookie seasons if you were to give Foles as many games played as Glennon. We have all seen what someone like Foles can do when given a proper coaching staff.
Then we have everyone who's available in the draft. Bridgewater will be taken #1 Overall. Period. Bortles will be Top 5, easily. That leaves who, Manziel? Johnny Football isn't a fit for the style of football Jeff Tedford is bringing to Tampa. Where Manziel is a run and gun scrambler, Tedford runs a more mechanical pocket passing game. I just don't feel a gamble like him would be worth it.
Plus, you have Jadevon Clowney, Anthony Barr, C.J. Mosley, Jake Matthews, and Sammy Watkins, who all play positions that the Bucs need more talent in. All excluding Clowney, but I say draft him simply to increase the Tampa Defensive Dominance. In short, there is simply too much talent that Tampa could very well make use of to use a round one pick to draft competition for Glennon.
So there, that is my case for allowing Glennon to play another season. I truly believe that with proper coaching, he could become one of the most dangerous passing threats in the NFL. Even if not, If he can even preform at an average level... well Lovie Smith took the Bears with Grossman under center. Grossman. If he took Grossman to a Superbowl, he can take Glennon to a dynasty.