It also freed quarterback Russell Wilson for a 14-yard scramble on a second-and-12 play early in the fourth quarter.
Was the hit within the rules? Replacement officials did not penalize Tate for the block. The NFL has not yet announced whether Tate would incur a fine. I suspect he will based on the following factors:
This play resembles others the league has cited in explaining its rules for blindside blockers on defenseless players. Lee was running laterally with his head turned back to the runner. He could not see Tate.
Rules prevent blindside blockers from striking defenseless players in the head or neck area. Tate did strike Lee in this general area, in my view, but he could still face a fine even if the league determines Tate did not strike Lee that high.
Rules also prevent blindside blockers from using the crowns or forehead areas of their helmets to deliver forcible blows to the defenseless player's body. Even if Tate did not strike Lee in the head/neck area, he did lower his head to strike Lee in the upper chest area. Tate's helmet hit Lee in this area.
Before 2012, these rules applied to blindside blockers approaching their targets while moving toward their own end line. The blindside blocker had to be approaching the defenseless player from behind or from the side. Starting this year, the rule also applies to blindside blockers approaching their targets while moving parallel to their own end line. Tate was moving parallel to the end line when he stopped and waited for the unsuspecting Lee.
What was Tate supposed to do, let Lee make the tackle? That is a common and reasonable question. Tate could have delivered a legal block by using his shoulder or arms to strike Lee in the upper body, beneath the neck/head area. That is my interpretation of the play, anyway. The league will offer its view at some point.
For reference, the rules prohibit contact against a defenseless player when it includes "forcibly hitting the defenseless player's head or neck area with the helmet, facemask, forearm, or shoulder, regardless of whether the defensive player also uses his arms to tackle the defenseless player by encircling or graspoing him; or lowering the head and making forcible contact with the top-crown or forehead/hairline parts of the helmet against any part of the defenseless player's body."