The Football Outsiders determined that, based on advanced statistical metrics, the Patriots' Tom Brady was the best quarterback in the NFL in 2009. The Chargers' Phillip Rivers was second, the Colts' Peyton Manning third and Drew Brees of the Saints fourth.
Why was Brady ranked above the others? According to the Football Outsiders, the defining factor was strength of schedule. Based on their numbers, Brady played the hardest schedule of pass defenses of any quarterback in the past 15 years.