I am not sure why anyone gets agitated over the Patriots running game. It has never been all that complicated. It only looks complicated when guys get hurt but people have specific roles and responsibilities. There is no secret formula or shroud of mystery.
Sure seems like Gray and Blount have interchangable roles.
Tough to predict when BB is going almost exclusively to the pass oriented RBs.
I agree with the first part, they do seem to share a role ( Ridley role of the past few seasons). I expect only one of them to have any relevance in a given game, barring injury. I expect it will be Blount.
Looking at the Pats running game performance over the past few years, they have been a productive backfield.
**2014 - Ridley / Blount / Gray/ Vereen combined for 1300 yards / 12 TDs ( ~320 carries )
2013 - Ridley / Blount combined for 1400/14 ( ~320 carries )
2012 - Ridley 1250 / 12 ( 290 )
2011 - BJGE / Ridley combined for 1100/12 (270)
2010 - BJGE - 1000/13
** 2014 is an outlier in the number of backs due to Ridley injury with no viable RB behind him. Vereen took a few weeks as starter, but gave way to Gray and then Blount ( gray went into the BB doghouse for oversleeping, IIRC ).
If you look more deeply, you see that these are not primarily accumulated by a workload share, but each back contributing to the total has a number of starts that roughly equals his percentage of yardage/tds. In other words, the NE backfield consists of two primary roles, the workhorse runner and the passing back. Barring injury or doghouse, BB will ride one back as his workhorse runner for around 300 carries, and that has typically produced ~1100 / 12.
I suggest that one of these guys is going to produce like a mid to high RB2. I just don't know which one ( though I suspect Blount ).