Kurt Warner
He played six years in St. Louis, with a nice three-year run with the "greatest show on turf," and a Super Bowl win, but not more successful than McNabb over the long haul. Fewer wins, fewer starts, fewer TDs, yards, Pro Bowls, etc. Also, Warner had Holt, Bruce, and Faulk (who was the best RB in the NFL at the time). Prolific offense. But after his six years in St. Louis, only three of which were good, he has been a journeyman. Nice job this year in Arizona, but he does have two of the best WRs in the NFL in Boldin and Fitzgerald.