I think it's a great topic! I'd like to weigh in on this one. Running backs both matter and don't matter. PFF, FO, and other analysts have all looked into this topic. Running backs typically are a product of their line. So if you have a good line you will get good RB production. Now sometimes that doesn't happen. Take Darrell Henderson's first year for the Rams or Antonio Gibson's first handful of games for the WFT. Both those guys had technical issues not knowing how and when to cut, hit the hole, press the line, etc. Their OLs were opening up holes but both those guys had issues executing. Both got better. Gibson by the end of last year had cleaned up his footwork and timing, same with Henderson in year 2.
To get into this in terms of the Patriots let's look at some stats:
Here is Sony's career grades via PFF:
Here are the Patriots line stats:
2018:
2019:
2020:
Let's look at those from football outsiders too:
2018:
2019:
2020:
What doe this tell us? It tells us that the Patriots have been one of the better run blocking teams the past 3 years. Whether it is PFF or FO or listening to guys like Brandon Thorn and Duke Manyweather the consensus has been clear that their run-blocking and overall OL play has been exceptional. They did have a dip in quality in 2019. It also tells us that Sony's production dipped when line play declined. That's normal. But we also see that Sony in 2018 and 2019 ranked in the mid to high 20's for open field rank. Open field rank is football outsiders way of showing how effective a RB is in space. We also see that with Sony at the helm the line was more helpful in creating yards than Sony. That Adj. line yards - rb yards tightened up with Harris leading the attack. So to me that indicates that Sony was more a product of the line (an exceptional line). Sony is a competent back. He took what was given to him but was not as successful breaking off long runs or creating opportunities himself. I think that supports the theory that if they had another competent back he would have produced similarly to Sony. That isn't a given. Rashaad Penny might not have worked out but Chubb probably would have! So arguing if they had just drafted any other back there is a dubious proposition. If they had signed a guy to be a starting back like say a Blount type he also probably would have worked out too given their OL. So while I believe
@rodderick is right that Sony's production probably could have been replaced with someone else it is not a given and to
@Soxy 's point Sony actually produced those yards in a competent manner which has to count for something.