Here is the sequence. Cover2 (the cb's were in man, two s over the top) and Manning steps up to take the free running TE that the MLB lets go with nobody to cover him. Jackson lets his man get past him as Manning tries to p/u the TE running free. Manning goes back to help when the pass is thrown but there are too many busts in coverage and its too late. The te is all alone on the fifty yard line....thats why Manning was compromised.
look on the 50 yard line