All our RBs looked good in preseason. And that may be more scheme than anything, but Robinson is a former 1,000 yard rusher and Williams is a former 1,000 yard rusher that led the league in TDs one year, so it's not like none of them have ever produced. I'm not convinced Perine is better than Robinson and Robinson got cut.
And Perine has never come close to 1,000 yards in a season. His best season was his rookie year at like 600 yards.