Wakefield captain Monty Betham has retired from rugby league to take up a career in boxing.
The 28-year-old joined from New Zealand Warriors a year ago and played in all but two of Wakefield's 28 league games.
"It is a blow but it was anticipated and it now allows one of our young players to step up to the mark," said Wildcats chief executive Steve Ferres.
"Although it leaves us short of cover, we have options at loose forward and in the back row."
Betham missed just two Super League games in 2006 because of a two-match suspension imposed for fighting.
Betham is the second New Zealand international to leave the Wildcats following their thrilling escape from relegation on the last day of the season.
David Solomona has now officially moved to Bradford.
Betham, who had another year left on his contract, will start out in the cruiserweight division and hopes to work his way down to light heavyweight.
Details of his first fight are expected to be announced in the new year.
Betham's father, also called Monty, had 53 professional fights as a middleweight or light heavyweight from 1973-82.