Haha, when you are in the NFL going against an athletic freak like JJ Watt you are anticipating him trying to blow by you, if he suddenly sits back you are not going to be able to suddenly attack him and "punch him in the gut.". He has to look to help out other lineman as there might be a stunt coming, head on a swivel.
He had enough time to look to his right to see if his Center was being beat. He had plenty of time to react to Watt. He just didn't process what was happening right in front of him.