Aftfer year 2 its unlikely a RB has a big breakout. Statistically the odds are very low, except for situations where a guy finally gets a shot to play. Mcfarland has been around for years, as has Harris.
They have been playing football literally 15+ years by now minimum, they don't just get lucky and have a magic switch flip giving them extra speed, power, vision or shiftiness. They are who they are.
I want to see more touches for Jaylen, he's never put out the bad tape.