Inside the day's key match-ups. The biggest star in the 68th edition of the Iron Bowl is obviously Alabama's thundering tailback, Mark Ingram, but with his nasty defensive counterparts, it's much easier to imagine the Tide winning without a particularly Heisman-worthy afternoon from Ingram or receiver Julio Jones than it is to picture Auburn pulling off one of the upsets of the year without its best effort on offense: The fact for the Tigers and the most generous defense in the S…