Tre Mason is a fair microcosm of the Rams' problems in the last four years in building out a roster and getting over the .500 hump.
In last year's roster preview series, I summed up the centrality of it in Mason's preview:
The bigger issue is how the Rams have managed themselves into this glut. They delayed playing Zac Stacy in favor of starting Daryl Richardson in 2013. Once Stacy proved to be the better back (which he was the entire time), Richardson was cast off.