Obviously Shanahan did an awesome job all year to get them to the point the game was pretty much won...then he calls a pass play on 2nd and 11 from the NE 23 (in FG range) with the game almost over. Only possible bad outcomes to the play would be a sack, incompletion (would stop clock), an INT or a fumble.
Best thing to do would have been run Freeman up the middle with the ball secure. Even if he gains no yards or loses 1 the Falcons still win (their kicker was 28/29 inside 50 yards this year). Why call a pass?
He also should have run it on the play Ryan fumbled...I think that was 3rd and 1 from about mid-field. Even if they don't pick it up and have to punt, they probably win since the Pats would have had to eat more clock to drive the length of the field.