from Martin Merk of IIHF.com,

Zetterberg played in Sweden’s first game against the Czech Republic but hasn’t practised since due to back problems. He missed yesterday’s practice and didn’t join his team either in today’s pre-game skate for the match against Switzerland.

Team doctor Bjorn Waldeback addressed the media and said Zetterberg has a herniated disc. During the pre-game skate it became known that he will not only miss today’s game against Switzerland but that he will be out for the remainder of the Olympic men’s ice hockey tournament in Sochi and will fly home.

“He is still suffering from his back injury and it is so painful for him that he can't be in it any more. It is Z who has taken this decision together with me,” Waldeback said. “I think it is the cumulative load. There was no specific thing that happened in the game. The issues came the morning after. These are nerve-related issues and they often come creeping in. It is not one specific injury.

"[The NHL doctors] totally agree with us. When you suffer from a herniated disc the way he does, you need to go home for a medical evaluation."

“I spoke with Z on the evening after (Wednesday's) game and he didn't show any signs of feeling the slightest pain,” Swedish head coach Par Marts said. “Of course it's nothing one wishes for, but we have to see the possibilities and look forward.”

a bit more on Team Sweden...