The way I see it, the biggest key is going to have to be to get to Warner. There is no actual solution to stopping Fitzgerald. He can get through jams at the line, he can outjump double coverage, and he can be deadly when given cushion... so the best way to stop him is to stop Warner.
When the Eagles were attacking Warner, Fitzs' production slowed. The Eagles had five hurries against the Cardinals (all of which came between 1:27 in the second quarter through 4:01 in the third quarter). During that span, Fitzgerald had only one catch for 14 yards, which was a dumpoff against a Prevent defense. The key is going to have to be to get to Warner... which I think PIT can do.