According to the article on NHL.com:
"Mr. Wisniewski delivered a retaliatory hit to the head of an opponent who never had possession of the puck," said Colin Campbell, NHL Senior Executive Vice President of Hockey Operations. "The fact that Mr. Wisniewski is a repeat offender also entered into this decison."It's obviously a stricter sentence than fellow repeat offender Alex Ovechkin got earlier in the week, for his actions against Brian Campbell, but it sends a clear message to the players of the National Hockey League: their conduct is being watched, and the League isn't going to put up with retributional or unsportsmanlike play.
It's interesting to note that Ovechkin protested his ruling - a mere two games - as being excessive, and now Wisniewski is doing the same. They both of course tried their best to appear contrite about what happened in the games.
"I am truly sorry that my friend Brent Seabrook was hurt on the play," Wisniewski said in a statement released by the Ducks.
Oh, really? If that's the case, you have a weird definition of friendship, Mr. Wisniewski. I don't think many people would call somebody a "friend" after that person came up and knocked them out cold.