4. Carson Palmer
Back in April of 2013, the Cardinals made a deal with the Oakland Raiders to acquire Carson Palmer, who had already had a fairly decorated career to that point. At 33 years old, Palmer was coming off one of his better seasons in the league, having thrown for over 4,000 yards despite the Raiders finishing with a losing record.
In that initial season with the Cardinals, Palmer would go on to throw for what was, at the time, a career-high 4,274 yards. The Cards finished 10-6 and the trade for Palmer looked like it was paying early dividends.
A couple of years later, in 2015, Palmer would have the best season of his career as he threw for 4,671 yards, 35 touchdowns and just 11 interceptions en route to a 13-3 record. That season, Palmer would lead the league in yards per attempt, air yards per attempt, yards per completion and total QBR.
When his Cardinals career was all said and done, Palmer would wind up sitting fourth all-time in franchise history with 16,782 passing yards. He threw 105 touchdowns to just 57 interceptions and went 38-21-1 as a starter.