There is a gap between Rob Kelley and Samaje Perine

ESPN's John Keim reports that “there remains a gap” between Washington Redskins rookie running back Samaje Perine and starter Rob Kelley. Keim notes that: “coaches say he's still thinking too much when running the ball, and learning when to juke a guy vs. just run over him.”
In 2014, Perine was one of the most elusive running backs in college football. He forced 74 missed tackles on 262 rushing attempts and earned an elusive rating (the PFF metric that uses missed tackle rate and yards gained after contact to measure a runner’s success beyond the point of being helped by his blockers) of 100.4, the sixth highest in the nation. However, his elusive rating has fallen every year since, to 79.2 (11th ranked) in 2015, to 55.4 in 2016 (36th ranked).
Perine logged 6 rushing attempts in his team’s preseason opener against the Baltimore Ravens. He failed to force a missed tackle and managed just 0.83 yards after contact per attempt, the lowest mark among Washington running backs.
Keim also notes that Perine needs to “work on becoming more consistent in protection.” Perine logged six pass blocking snaps in his debut, and surrendered one pressure. His pass blocking efficiency of 87.5 ranked sixth of eight running backs with at least six pass blocking snaps.