Stranger things have happened.
Jeff Weaver was a 4.58 ERA, 96 ERA+ pitcher by the time the Cardinals acquired him. Doesn't scream "top of the rotation" to me. Neither does "86 MPH" Suppan, Jason Marquis or Anthony Reyes.
Offensively, this team will have no issue. They have firepower. "It's the pitching, stupid" as the famous phrase goes. My only point is that the 2006 Cards (who honestly had poor starting pitching, that's not debatable) are proof that sometimes wonky s*** happens during the playoffs.