"Our understanding is that Sona signed a letter of intent after the World Cup with a club," said Chiefs chief executive Gary Dawson.
But despite what appears to be the inevitable loss of a much-loved and important figure, Dawson said he was confident the Chiefs were handling player retention well and were hopeful they wouldn't see huge numbers depart at the end of the season. That's as much good news for the New Zealand Rugby Union as it is the Chiefs. After several outstanding years of keeping the top players in the country, the NZRU lost its first major battle in some time when Jerome Kaino opted for Japan.
The national body also fought hard to keep Jimmy Cowan who is going to Gloucester and appears to have conceded defeat with Isaia Toeava as well.
The Blues utility back is likely to go to Japan if he recovers from hip surgery.
The NZRU is wary of losing significant numbers of experienced test campaigners in one year.
The All Blacks were perhaps fortunate in 2008 that by the Tri Nations, the key players in their preferred side avoided injury to prevent the lack of depth from being fully exposed.
With the World Cup in the possession of the All Blacks, the NZRU is conscious of the commercial opportunity that presents. It has pressed home the even greater need for the All Blacks to maintain and enhance their reputation this year. Although Cowan hasn't been at his best so far, he'd still be a handy man to have around if injury strikes others.
Already gone from the World Cup squad are John Afoa, Brad Thorn, Kaino, Cowan, Stephen Donald and Mils Muliaina. Toeava is likely to follow and Sonny Bill Williams is coming off contract. By the end of the year, more than one third of the champion squad could be gone with other promising players also heading offshore.