I'm with Waks on this one, pretty much from start to finish.
Yeah, Priest had a great o-line, but he also played on a team that had virtually zero threats in the passing game. His first season with KC in '01 -- the year prior to Roaf joining the team, by the way -- Holmes rushed for 1,555 yards on 327 carries for 4.8 ypc. He also finished second on the team in receptions (62) and yards (614) ... behind Tony G.
And don't tell me that Derrick Alexander, Snoop Minnis, Larry Parker and Chris Thomas on the outside opened up the running game. Trent Green (24 INT's that year) wasn't scaring anyone, either.
Priest put up those numbers against defenses who were geared to stop him, and only him. They knew every play was going to be either a Priest run or a a dump off pass to Priest in the flats -- and still couldn't stop him.
Not bad for a guy no other team wanted that off-season.