I remembered Bolden getting non-garbage rushes last season but maybe it was an illusion since it's not on his game log, and he did even less in 2016. My memory must be faulty.
I'm less convinced of the difficulty of the Patriots system on running backs. I also think Patriots fans tend to underestimate the impact a quality running back can have on a game. I wouldn't be surprised at all if the Patriots take a day 1 or day 2 back in this draft. Sure, you can get a workaday guy like Gillislee for $1.5 million but you probably won't get a real stud outside the draft.
Well, in week-16 v. the Bills, Bolden got some snaps and 2 carries (20 yards) after Gillislee got hurt. Gillislee was already subbing for White and Burkhead who were inactive for that game due to injuries. Then, in the week-17 finale v. the Jets, Bolden saw 9 carries (46 yards) and 4 tgts (1 catch for 7 yards) in the second half during "resting the starters mode".
Prior to that he'd only gotten a few snaps, and only 2 carries (at the end of the Pats' 41-16 blowout of the Broncos).
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Whether the Pats' system is unusually "difficult" or not on RBs (although there's certainly a lot for them to learn, just in pass-pro alone), I believe it's the system - and an RB's thorough grasp of it - that has enabled the Pats' "non-stud" RBs to produce stud-like games (or close enough for the Pats' purposes) with fair regularity.
There's nothing that guarantees that an RB taken in the 1st or 2nd round WILL become a "stud" in the NFL, just as there's noting that guarantees that an RB like Kareem Hunt (#86, 2017) or Jordan Howard (#150, 2016) WON'T become a stud. It's way more a matter of finding the "right guy" for the system than it is drafting a prospect early.
More importantly, how much is really to be gained from spending a high pick versus a later pick (or from spending a pick at all)?
Fournette (#4, 2017):
... 269/1040 yds, 9 TDs rushing ... 36 of 48, 302 yds, 1 TD receiving
Hunt (#86, 2017):
... 272/1327 yds, 8 TDs rushing ... 53 of 63, 455 yds, 3 TDs receiving
Jordan Howard (#150, 2016):
... 232/1313 yds, 6 TDs rushing ... 29 of 50, 298 yds, 1 TD receiving
Dion Lewis, 2017:
... 180/896 yds, 6 TDs rushing ... 23 of 35, 214 yds, 3 TDs receiving
While it's nice to think that a (potential) "stud RB" drafted in the 1st or 2nd round would make a huge difference to the Pats offense, from a cost-effectiveness perspective, it's highly unlikely.