Rugby: Sonny Bill Williams cops four-week suspension

All Blacks midfielder Sonny Bill Williams has been suspended for four weeks after pleading guilty to unnecessary contact to the head at a judicial hearing this afternoon.

Williams became the first All Black in 50 years to be sent off after his shoulder connected with the head of Lions winger Anthony Watson in the All Blacks' 24-21 defeat last night.

Now, he will miss the third and deciding test.

"Sonny is disappointed. Not for himself. He accepts that he made a mistake and he's disappointed that he has let the team down," said All Blacks coach Steve Hansen.

"The mantra is that the team comes first and he knows he has let them down. But we can't go back and change it either. People make mistakes. It is a fluid game. It is a fast game and unfortunately he has made a mistake and we have to move on from it."

The All Blacks have called Malakai Fekitoa into the squad as Williams' replacement.

Before leaving for a flight to Auckland, Williams said he was disappointed at his actions and that he felt he let the All Blacks down.

"Obviously I'm really disappointed but happy to be able to get in there and say my piece," Williams said afterwards. "They've come to the conclusion that it was reckless, that it wasn't intentional. I've got in contact with Anthony and I've apologised to him but I'm very disappointed that I was sent from the field last night and that I let my brothers down."