Worse than the drop was his gaffe that negated it.
I'm pretty sure Vrabel failed to report, causing the formation to be illegal when he covered up the last man on the line of scrimmage, while wearing a number between 50 and 79. He also was an inelligible man downfield, but the illegal procedure came first.
The NFLN guys showing the replay didn't have a clue, but the reason the flag came so late was probably that the refs had to caucus to see if he reported. Vrabel also is pointing to his number as he's running off the field.
You'd think for all his offensive plays he'd remember that, particularly in a big spot. Good for Maroney for picking up the team in a big spot!