The St. Louis Rams surprised many people (me included) when they drafted Tre Mason from Auburn in the 3rd round. There wouldn't be much surprise if the Rams didn't already have a solid starting running back on the roster in Zac Stacy. Since the Rams drafted Mason during the 2nd day of the draft they must see something in him that they didn't already have on the roster.
Change of pace guy
From what I've seen from Mason, he does have speed. It's not blazing Chris Johnson speed, but it's enough burst and speed for some big gains during the season.
Don't expect Mason to be a pass blocker on 3rd downs unless he dramatically improves. He wasn't assigned to block much with Auburn. And when he did, it wasn't pretty.
The gif above was the best pass blocking that I've seen from him.
He will, however be expected to catch some passes.
Sam Bradford has no problem checking down when he doesn't think a receiver is open. Note that, from 2012-2014, he only caught just 18 passes. I'm not saying he can't do it, but you would like your scat back to be able to do that.
"I've been waiting for him to come off the board. He gets north; he gets south. He played so well in the national championship game and caught peoples' eyes. Mason has jump-cut lateral quickness to accelerate up the field. The only thing I don't like is his pass pro. The next time he blocks somebody in pass pro will be the first time." -- Mike Mayock
Mason does have kickoff experience under his belt. He didn't return many kicks last season, but he does have a noteable kickoff for a touchdown. The Rams have needed a kickoff returner for years. He's probably the best option that the Rams have back there. Plus, if Mason proves to be a solid returner, that would probably free up a roster spot for the Rams 53 man roster.
Lack of solid depth
Zac Stacy is the starter. As he should be. He had good rookie season. After Stacy, however, the running back situation is murky.
Benny Cunningham showed promise, but he's had some injury problems and he might be best as a backup running back or depth guy.
Coach Fisher put his foot on Isaiah Peads' career and threw it off a bridge without a lifejacket, so it's doubtful that he'll be on the final 53 man roster.
Stacy has had his share of being nicked up during the season. When you look at the Rams depth at running back it makes perfect sense that the Rams will add another running back to the roster, and one that has a different skill set than the backs already on the roster.
Mason doesn't run like a typical scat back, but he probably has the best speed of the ones currently on the roster. The one thing that surprised me is that he's a tougher runner than I originally thought. He can hit outside stretches, but defenses will also have to worry about him running between the tackles. Mason and Stacy should be a good one two combination.