Whitner wasn't penalized because the tackle wasn't against a defenseless player. Helmet-to-helmet hits are banned against defenseless players in eight categories, and a runner isn't one of those categories. Thomas was considered a runner because he'd made a catch, turned and made a "football move" before being hit.
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The eight categories were incorporated into one new rule last March, and a new rule extended the protection for a receiver who has completed a catch until he has had time to protect himself or has clearly become a runner. Thomas had become a runner.
The eight defenseless player categories are:
» A player in the act of or just after throwing a pass.
» A receiver attempting to catch a pass; or who has completed a catch and has not had time to protect himself or has not clearly become a runner. If the receiver/runner is capable of avoiding or warding off the impending contact of an opponent, he is no longer a defenseless player.
» A runner already in the grasp of a tackler and whose forward progress has been stopped.
» A kickoff or punt returner attempting to field a kick in the air.
» A player on the ground at the end of a play.
» A kicker/punter during the kick or during the return.
» A quarterback at any time after a change of possession.
» A player who receives a "blindside" block when the blocker is moving toward his own end zone and approaches the opponent from behind or from the side.
The competition committee that recommends rules changes could re-examine such hits during the offseason.
Thomas, who didn't return to the game, posted on his Facebook page Sunday morning that his head injury isn't an issue.
The Associated Press contributed to this report.