Hamilton - Newly crowned New Zealand heavyweight champion Sonny Bill Williams may miss the Chiefs opening 2012 Super Rugby match against the Highlanders.

The Rugby World Cup-winning All Black, who defeated Clarence Tillman III with a first round technical knockout last week, suffered a minor injury while training.

Undergoing sprint training in Sydney while based with Tony and Anthony Mundine leading into the fight, it was revealed that the extensive workload - rugby specific conditioning during the day and boxing work at night - took its toll on Williams.

The hamstring twinge has been revealed to be nothing more than a minor tear, but it is something that the Chiefs will not want aggravated before the season begins.

Chiefs coach Dave Rennie said that Williams has not been a full participant in the team’s training so far, with the Waikato-based franchise beating the Highlanders 38-36 over the weekend.

"He's been fine," Rennie said.

"We've been conscious of the fact that he's been smashing himself at night in the boxing gym so we've taken him out of some of our conditioning stuff. He has been doing our skill-based work and he's got a pretty good idea of what we want to do."

"We gave him last week off to concentrate on his boxing but he has been running with the team."