The National Hockey League has suspended San Jose Sharks defenseman Brad Stuart for three games for his illegal check to the head against New York Rangers forward, Rick Nash. The hit occurred early on the in the first period, and the Rangers received a two minute power play as a result of the hit.
Nash remained in the game for the remainder of the first period, but wasn't present when the Rangers took the ice for the second period.
Nash stated after the game that he had a headache following the hit, and it continued to get worse as the period went on. There has been no official update from the team at this point in time, so we don't really know the severity of the situation. It could have been a precautionary move, or Nash could have indeed suffered a concussion. We'll likely find out more tomorrow when the Rangers take the ice for their morning skate.
Here is the official video from Brendan Shanahan, which explains their reasoning behind the suspension.