The 2012 Jets are not losing because Mark Sanchez has failed to live up to promises made in the past. The Mark Sanchez of 2012 is about equal to the rookie version of 2009, who went to the AFC title game. He has slid from the 2010 version, which beat the Colts and Pats in the playoffs, but not nearly enough to explain the team's overall decline from an 11-5 record that year.
Here is the real difference between those Jets and the current model: The 2009 team ranked first in the NFL in rushing offense and first in defense. The 2010 team ranked third in defense and fourth in the run game. This year: 16th in the run, 17th with its Darrelle-Revis-depleted defense.