That's kind of the play. You literally get a fraction of a second to move forward. Any longer and typically you have LBers flying to the play. Those pushes and holes close quickly atound the goal line
See, he doesn't get the benefit of taking his time and watching on a slow motion replay from his couch. These plays have to happen fast. Dawkins (and Feliciano) failed miserably to get the push the play called for. Picking that side is not on Allen...it's squarely on Simmons wanted to make the stop more than Dawkins wanted to stop him from doing it.