I know arm strength can be overrated in importance but I don't think I've ever seen a QB with a weaker arm than Matt Barkley with the possible exception of Chad Pennington.
His arm is weaker than Matt Cassel's, Fitz', Orton's, McCoy's, anyone's. It's screamingly obvious AFAIC.
All you have to do is watch the video and it jumps off the screen… and I intentionally only watched his games from 2011 when he was completely healthy and had a great season.