Carolina's 5 primary RBs last year in terms of YPC. USC had 5 RBs with over 20 carries, and Williams was the only one to average fewer than 5 YPC at 4.7. The other 4 combined to rush for 1495 yards on 276 carries for a very impressive 5.42 YPC. Ty'Son ran for 328 on 70 carries, for 4.69 YPC. All of them are back next year, and 3 of the other 4 are very similar back to Ty'Son, which is why I assume he left.
All that said, I think he's a good back and will probably be the best back on the team, but if you're comparing him to other backs then it probably makes sense to look at how he stacked up on his own team.