https://www.profootballfocus.com/about/history/started officially in 04 but from what I was able to find out, went back several decades to come up with the grading formula's, whether that includes or excludes Barry etc I have no idea.
I spent time trying to get actual numbers posted, but while PFF continually makes reference to him, a breakdown of actual missed tackles is missing. So in essence PFF did study him, however, my guess is they didn't watch all the games ofcarrier so data isn't complete. Either way, pretty damn impressive.
Edit: after further researching this subject it becomes apparent that there was really not much actual breakdown other than specific historical accomplishments which sad to say missed tackles isn't. For my money Sanders is the greatest back I've ever watched in person, and as much as I love the way Lynch plays, I don't see that opinion changing. Barry simply IMHO was the best ever ( and I know many feel it was Brown or Sayers or Payton, with valid reasons, hell my son insists Smith was the "guy" even though he never saw him actually play live. But again IMHO Smith falls below the ones mentioned in my book, and to be honest, if Lynch has two more seasons at the level he is at now, I might rank him above Smith as well). That all said, still pretty damn impressive, McCoy finished second last year by 20 missed tackles, which is approximately a full 1/4 less missed tackles which is INSANE in my book.