The team's web site confirmed they were on the injury report, but all participated fully. Along with them, right tackle Marcus Gilbert (groin) also participated fully after being limited Monday.
The reason all three are important centers around the running games, both offensively and defensively. Harrison and Polamalu are irreplaceable against the ground game, giving the Steelers an anchor on the offensive left side (Harrison) and sideline-to-sideline speed to pursue ball carriers (Polamalu).
Mendenhall could be optimistically seen as having the ability to bust the Steelers out of a rushing slump its been under through three games this year. His contributions may not have the most obvious immediate results, due to the physical condition of his knee. Realistically, though, it wouldn't take much to improve the running situation; wide receiver Antonio Brown (6.0) and quarterback Ben Roethlisberger (4.0) lead the team in yards per carry.