I agree with Xpanda and Grand Master that Clayton is the way to go. It's tough to sit Ward, especially off last week, but you must play each week differently based on matchups.
The Packers could have the worst secondary in the NFL. Both Clayton and Joey Galloway are good plays this week. The Packers probably will try to take away Cadillac Williams, so they won't be able to give much safety coverage to Clayton.
The Steelers, on the other hand, are going to pound the ball against the Patriots, which is the way to beat them now that they no longer have several of their good inside linebackers. This is going to eat a lot of clock. Ward isn't going to get easy TD's like he did against the Texans' weak secondary.