I'm sure they had it hammered into them right before the play to make sure there is NO PASS INTERFERENCE. So of course if your coaches drill that into your head before the play, that is what your thinking as you go to make the play. He got there just a split second early and decided to play it "safe" and avoid the PI call, assuming he would have had help from the CB or it'd be incomplete.
I feel bad for the guy, b/c he had a great year for a rookie. You can't blame the game on him, plenty of other reason's as to why the Saints lost, but obviously that is the most glaring play and he's on the wrong end of it.