Not the first time he's gotten this accolade.
PFF uses a complex formula of Missed Tackles, and Yds After Contact, to rank NFL rushers.
This excerpt says a lot:
perhaps the most impressive mark was from Jonathan Stewart of the Panthers. Stewart only carried the ball 142 times (less than half of the carries of some of the players ahead of him, but he forced 32 missed tackles as a runner and added another 20 on his receptions for a total of 52. The Panthers have brought in Mike Tolbert in free agency this year to potentially replace Stewart if they can’t lock him down long-term, but they may not fully appreciate exactly how capable he is of making plays independent of the blocking in front of him. If Stewart makes it to the open market next offseason, he may not be in line for big money given the way running backs are viewed in today’s league, but he will make a huge impact wherever he ends up.