Let's see...
Hardly ever played under center in college...will need to play under center in the nfl...
Ran a hurry up spread in college...will need to run a pro style offense in the nfl...
Bailed out by giant wide receiver in college...current giant wide receiver might be suspended for a year...
Had very good athleticism compared to the typical college player...in the nfl there will not be a single game where he is the most athletic...maybe even 2nd or 3rd most athletic person on the field...
Got drafted to a team that has been churning and burning QB's for nearly half my life...Brian Hoyer might legit be the best QB the browns have had in the last decade...
All these things combined...if Manziel makes it to a second contract I will be surprised...if his second contract is bigger than his rookie contract I will be outright shocked...