Marvin made the mistake of not performing in practice. He was one of my favorites based on one catch and a couple of runs he made last year when he played a little. Clearly he wasn't getting it done and didn't think he could eat out Ervin, Yant and Stepp. Belt playing instead of Marvin told you all you needed to know either about his ability or his mental make up. I'm not sure how we could say it's because it was because he wasn't a walk on when we've seen the most consistent QB we have never get a shot and yes he's a walk on.