To be honest I have never studied all of Mannion's college game film like I did with Goff so I'm not going to pretend I have a deep in depth opinion of his game/potential.
I was caught off guard when the Rams drafted Mannion in the 3rd round (No. 83). I thought it was too high at the time but after reading about him I realized it was his Junior season that pushed him up the draft for some teams and the fact that he ran a pro scheme offense.
Clearly his best year was 2013 because his O-Line was far superior to what he had in 2014 and his best WR Brandon Cooks was on that 2013 Oregon St roster.
Anyway I watched a few of his games from the 2013 season and I was impressed and thought he showed some potential to be a quality backup or a possible starter if he was surrounded by a strong supporting cast. I know that can be said about half the quarterbacks drafted...
He did show some talent in his 2013 film and if Mannion had declared for the draft after his Junior season and was drafted by the Rams in the 3rd round, I wouldn't have been caught off guard or thought of him as a bit of a reach like I did.
2013 Comp 400
Att 603
Comp% 66.3
Yards 4,662
YPA 7.7
TD 37
INT 15
Rating 146.6
View: https://www.youtube.com/watch?v=rIzBlJNMgX0
View: https://www.youtube.com/watch?v=Y65X3GPIadk
View: https://www.youtube.com/watch?v=MAdQLCwKBO8
View: https://www.youtube.com/watch?v=s0W0MnAS_Kc
Draft Bio (I read that some scouts liked him more than this draft bio so don't be offended
@Dxmissile
ANALYSIS
Four-year starter who owns 18 passing records at Oregon State. Tall quarterback who sees over the offensive line. Throws with high release point. Plays with desired footwork. Can sit down and shift weight properly to drive the intermediate throws. Played in pro-style offense and is comfortable with 3-, 5- and 7-step drops from under center.
When protected, shows confidence to stand and deliver with accuracy to all areas of the field. Trusted by head coach Mike Riley to make pre-snap reads and audible. Played in multiple-read offense and shows patience in allowing routes to develop. Good feel for pro-style play-action passing attack and can throw with above-average accuracy and ball placement.
WEAKNESSES
Tempo of his play is a concern. Slow in takeaway from center and set-up and slow getting through progressions. Carries ball low in the pocket, allowing defenders to swipe at it. Finished career with 30 fumbles and 54 interceptions. Poise and mobility in pocket are below average.
Not considered a play-extender outside of pocket. Drops eyes and misses throwing windows when he senses pressure around him. Decision making greatly influenced by level of pressure around him. Fails to throw with adequate zip when feet aren't under him and he doesn't step strongly into throw. Takes too long to get rid of throws on out routes.
DRAFT PROJECTION
Round 5 or 6
SOURCES TELL US
"His stats and tape weren't as good this year as last year, but he flashes NFL potential in every game you watch. I thought he did the same thing at the Senior Bowl practices." -- NFC area scout
NFL COMPARISON
Matt Schaub
BOTTOM LINE
Tall, rhythm thrower who shows an ability to play with confidence and accuracy when used as a game manager within an offense featuring a strong rushing attack. Mannion needs plays to stay on schedule or his confidence becomes shaky and the turnovers start rolling in. Mannion lacks arm talent to carry an offense, but has enough ability to become a capable backup.
http://www.nfl.com/draft/2015/profiles/sean-mannion?id=2552576