No one thought Kurt Warner was a franchise savior when he started playing for the Arizona Cardinals at 33 years old. He was viewed as a tough, smart quarterback who was broken down and nearing the end of his career. He was an option to start if younger guys (first Josh McCown, then Matt Leinart) didn't pan out.
Opinions weren't exactly changed when the Cardinals went 2-8 with Warner starting in 2005, even though he had some nice moments.
Our perceptions of a quarterback's efficiency too often are colored by his win-loss record. Palmer is viewed as some sort of "reclamation project" because the Oakland Raiders struggled so badly in 2012. But Palmer mostly was the guy we've seen for years: An average NFL starter with the capability to make some terrific throws and some bone-headed mistakes. Palmer's not a guy that lifts the players around him, but he can be successful if the team around him is strong -- and the Cincinnati Bengals and Raiders didn't provide much support for Palmer.
Palmer's numbers with the Raiders were similar to the ones he had on the Bengals. Warner's career path was much different. He started out like gang-busters for the St. Louis Rams, struggled with injuries and then played down another level while with the New York Giants (although it's easy to forget Warner played better than you remember for the Giants.)
The recent history of veteran quarterback additions is not pretty. Even when they work, they don't work for long. Brett Favre did better than expected playing for the Minnesota Vikings. Chad Pennington had a brief resurgence with the Miami Dolphins. But no one has peaked again for a second time quite like Warner did with the Cardinals.
The Cardinals are a better team with Palmer. I like the trade plenty and think it could work. If they weren't in the NFC West, the Cardinals might even have a chance to contend for a playoff spot because of a strong defense. But Palmer never consistently has displayed difference-making ability since he tore his anterior cruciate ligament in the 2005 playoffs. Warner's touch, accuracy, toughness and football intelligence were special for the Rams and Cardinals. He was a perfect fit for coach Ken Whisenhunt and offensive coordinator Todd Haley's system in Arizona.
Palmer might fit well with coach Bruce Arians' bombs-away approach, but he's a long way removed from his peak. And his peak was nothing like Warner's. There's no reason to expect veteran quarterback lightning to strike twice in Arizona.