A hugely talented centre, Williams caused a media storm in 2008 when he walked out on NRL side Canterbury Bulldogs to switch codes with ambitious French side Toulon.

A Kiwi rugby league international, Williams' move was eventually secured thanks to the payment of a £300,000 transfer fee. He started slowly in union, but his strong running game soon saw him win plaudits and a regular place in the Toulon side and it was not long before he was touted as a possible All Black.

He represented the Barbarians against Australia in 2009 - the first time that he had returned since his controversial spilt from the 13 man code - and following his second season in France's top flight he opted for a move back to New Zealand with Canterbury and the Crusaders. Williams reportedly turned down the most lucrative deal in the history of professional rugby in favour of furthering his chances of becoming a dual international.

Williams' bow in New Zealand rugby was delayed by injury, but he made an immediate impact on Canterbury's ITM Cup campaign. He showcased his dazzling attacking repertoire but was also criticised for several defensive lapses. Nevertheless he secured a maiden call-up to the All Blacks squad for their end of year tour and made his international bow against England at Twickenham at outside centre. He was switched to the No.12 shirt for the game against Scotland at Murrayfield and collected the Man of the Match performance thanks to an outstanding all-round display.

He has also embarked on a career as a boxer with his first professional bout - a second round TKO win - taking place in 2009 with his second fight also going the same way in 2010. A stress-related leg injury picked up on the All Blacks' end of year tour limited his preparations for the new Super Rugby season but did not prevent him from extending his winning run in the boxing ring at the start of 2011.

When his belated Super Rugby debut came, he did not disappoint, scoring a try in a thrilling performance for the Crusaders against the Waratahs in an emotional game following the devastating Christchurch earthquake. He returned to the ring later in the year, as part of a fund-raising push following the quake, and won a six-round bout on points.

Williams played his part as the Crusaders reached the final of the Super Rugby competition, but they lost in the final to the rejuvenated Reds franchise. Williams took his place in the All Blacks squad for the 2011 Tri-Nations.

With rumours surrounding Williams' future, the centre made the announcement in late August that he would delay any decision over where he will play his rugby in 2012 till after the World Cup. After being dropped from the All Blacks squad for their Tri-Nations decider against Australia, Williams went into the World Cup with much to prove.

Williams endured a mixed campaign for the All Blacks with Ma'a Nonu and Conrad Smith the preferred combination. He was predominantly used from the bench but started three of their matches - scoring four tries in the process. And against Australia in the semi-finals of the tournament, Williams came on from the bench only to be yellow carded three minutes later.

And after lifting the World Cup, Williams announced he would join the Chiefs on a one-year deal. But soon after the deal was confirmed, Williams was rumoured to be looking to Sydney in a potential cross-code switch for the 2012-13 season.

Williams fought his sixth professional fight in February 2012 when he beat Clarence Tillman III in a first-round knockout. This followed the pre-match weigh-in where Tillman landed a punch on Williams while facing up to each other.