The key to the game is going to to be the ability of the Steelers linebackers (Farrior, Foote, and Timmons) to cover the Cardinals Running backs and wide receivers in space underneath. Warner makes a living beating the blitz but when he does beat the blitz he almost always goes underneath. I don't think Warner will have enough time to look deep to Fitzgerald if Polamalu, Woodley, and Harrison are breathing down his neck.
Offensively I think the Steelers will employ a gameplan similar to the one they used against San Diego. Pound Parker early and go deep to Washington, Holmes, and Sweed later in the game off of play action. Parker will look to get to the edge when the Cardinals defense begins to tire during the Second Half. I really think Parker can run on this defense which is speedy but not physical like Baltimore or Tennessee.