There's a reason they were the 2nd and third guyTrue. But you also touched upon another key factor -- they were in a platoon [and in Howard's case, the third guy in the platoon]. You can't just look at it and say, Adams got 327 yards -- ergo, he's not good enough. He was the second guy.
If they were better he would get the bulk of the carries, 327 yards in college shouldn't get anyones minds on the NFL, you need to actually produce in college