2008–10: Toulon In July 2008, after linking up with new manager
Khoder Nasser, Williams left Australia to join the
Tana Umaga coached French rugby union club Toulon. In his controversial mid-season exit from the NRL, Williams cited
salary cap concerns for his move. The Canterbury Bulldogs club officials and players were not notified of his departure until after Williams had already left for Europe using a Samoan passport. Williams was eighteen months into a five-year contract with the Bulldogs, and the dispute was only resolved when Toulon paid a transfer fee of around £300,000 (A$750,000). According to the Bulldogs
CEO Todd Greenberg, Williams was "our best player [before he] walked out". The circumstances in which he left the Bulldogs created a media debate in Australia and New Zealand, and Williams was the subject of considerable criticism for a departure that was described as the greatest act of treachery in the game's history. Williams's highest honour with Toulon was finishing runner-up in the
2009–10 European Challenge Cup. On 6 June 2009 he played for
the Barbarians in a tour match against
Australia. His contract with Toulon ended in June 2010; in the same year Toulon reportedly tabled a three-year, $6 million offer to Williams, while the
New Zealand Rugby Union (NZRU) came up with a $550,000 per year deal. He was also offered the chance to play for
France at the 2011 World Cup. He then chose to play with Canterbury in the
ITM Cup and the Crusaders in the Super Rugby competition.
2010: Canterbury On 3 September, Williams made his Canterbury debut against
Bay of Plenty after previously playing for the
Belfast Rugby Football Club in the
CBS Canterbury Cup. He was named in the reserves and eighteen minutes into the game replaced second five-eight
Ryan Crotty. Williams scored his first try in Canterbury's ITM Cup loss to
Taranaki; he followed up with tries against
Wellington,
Otago and
Counties Manukau. On 9 October, Canterbury became the new holder of the
Ranfurly Shield, and on 5 November they were crowned ITM Cup Champions after defeating
Waikato 33–13. On 17 October, Williams was named in the
All Blacks squad to tour Hong Kong and the Northern Hemisphere. This would make him only the fourth person to have played for the All Blacks before having played any Super Rugby, since Super Rugby exists. He made his highly anticipated New Zealand debut at
Twickenham against England on 6 November. He started at outside centre and combined with
Ma'a Nonu to form the heaviest ever All Black midfield partnership at . In playing for the All Blacks he became the first person since
Karl Ifwersen, in the 1920s, to represent New Zealand in rugby union after first playing for New Zealand in rugby league. On 13 November, in his second game for the All Blacks, Williams was awarded the
man-of-the-match for his performance against
Scotland.
2011: Crusaders On 4 March, Williams made his
2011 Super Rugby debut for the Crusaders against the
Waratahs, scoring a try and setting up another. A week later he scored his second try against the
ACT Brumbies. On 27 March he returned to Twickenham to play against the
Sharks in the first Super Rugby match played outside of New Zealand, Australia or South Africa. On 9 April, in his fifth game for the Crusaders, Williams scored his third try. On 23 April, Williams, playing off the reserves bench against the
Highlanders, experienced his first rugby defeat since his All Black debut more than five months earlier. A week later he scored his fourth try while playing against the
Western Force. On 7 May, Williams played his first rugby match in South Africa, in the Crusaders' victory over the
Stormers at
Newlands Stadium. On 29 May he played against the
Queensland Reds in a match which set a new attendance record for an Australian Super Rugby game, with 48,301 fans at
Suncorp Stadium. On 25 June he scored his fifth try while playing against the Sharks in the first finals week of the Super Rugby competition. A week later, against the Stormers in
Cape Town, he was part of the Crusaders team that became the first side since 1999 to win a Super Rugby semi-final outside their home country. On 9 July, Williams was part of the Crusaders team which lost to the Reds in the grand final, held at Suncorp Stadium before an Australian provincial attendance record crowd of 52,113. He ended the Super Rugby season with the most off-loads, was second to
Quade Cooper for line-break assists, was in the top ten for try assists and was 13th overall for run metres—no other centre came close to Williams's off-load and line-break assist figures. During his time in Christchurch, Williams was present when both the
2010 and
2011 Canterbury earthquakes struck. On 30 July, Williams played his first home
test match during the second game of the
2011 Tri Nations Series. On 9 September he played in the
opening match of the
2011 Rugby World Cup. A week later he scored his first test rugby tries during New Zealand's
second game, in which he played on the right
wing. The match was also the first time he had played outside the centres since playing in a handful of games on the wing and in the back row for Toulon. He scored his third try of the tournament
against France, in his second consecutive game playing on the wing. On 2 October, Williams scored in his third consecutive match, whilst playing
against Canada. New Zealand went on to win the tournament, with Williams amassing a Rugby World Cup record of three tries as a substitute player. On 31 October it was announced that Williams would join the
Chiefs for the
2012 Super Rugby season. His new contract allowed a "limited number" of professional boxing bouts.
2012: Chiefs On 25 February, Williams made his
2012 Super Rugby debut for the Chiefs against the Highlanders, In early March he was named as the NZRU's
Teen Rugby Ambassador. On 14 April, Williams scored his first try for the Chiefs while playing against the
Cheetahs. On 13 May he scored his second try in the Chiefs' first loss since their club record of nine consecutive wins. On 2 June he scored his third try while playing against the
Blues. During the
mid-year rugby test series, Williams played in all three of New Zealand's matches
against Ireland, scoring two tries in the last game of the series. On 6 July he scored his fourth try for the Chiefs—this time against his former club, the Crusaders. On 4 August, Williams played in the Chiefs' 37–6 victory against the
Sharks in the
Super Rugby final, scoring the last try of the match then celebrating by leaping into the home crowd. With this victory, Williams became only the fourth person, after
Peter Ryan,
Brad Thorn and
Will Chambers, to have won both an NRL and Super Rugby title. He also ended the season with the most off-loads (for a second consecutive year), most tackle busts, most line-breaks and most turnovers gained. He was also awarded the Chiefs' players' player award. On 18 August, Williams played for the All Blacks in the
first match of the inaugural
Rugby Championship. The following week, he ended his two-year tenure in New Zealand rugby with a man-of-the-match performance in New Zealand's
Bledisloe Cup winning
22–0 victory over Australia.
2012–13: Panasonic On 9 July 2012, Williams announced he would be playing for the
Panasonic Wild Knights in the Japanese
Top League during the
2012–13 season—with the allowance to have one boxing fight during the season—before returning to rugby league. The Panasonic deal was thought to be the largest one-season contract in rugby union history. He was also expected to be heavily involved in the promotion of the
2019 Rugby World Cup in Japan, the country being the main host of the event. On 9 September, a week after sitting out the Top League season opener to be given time to adjust after coming off recent All Blacks duties, Williams made his debut for Panasonic against
NTT Communications Shining Arcs. On 22 September he scored his first try for Panasonic, while playing against
Toshiba Brave Lupus. On 27 October, Williams scored his second try during Panasonic's
eighth round victory over the
Kintetsu Liners; however, the match would be his final game of the season after sustaining an injury when he landed awkwardly on his shoulder following a tackle.
2014: Counties On 20 December 2013 it was announced that Williams would return to rugby union with the Chiefs on a two-year deal starting in 2015. He also aimed to represent New Zealand in the
2015 Rugby World Cup and in
rugby sevens at the 2016 Summer Olympics. On 15 June 2014, Williams signed a two-year deal, starting in 2015, to play in the ITM Cup with
Counties Manukau—reuniting with his former Toulon coach Tana Umaga. However, on 8 October 2014 he started his contract with Counties a year early when he made his debut for the club
against Auckland, only twelve days after his last game for the Roosters. He played the following game, which was also his club's final game of the season. On 20 October, Williams was named in the All Blacks' squad to
tour the US and UK in November. On 1 November, he made his return to international rugby against the
United States, scoring twice in a man-of-the-match performance. He went on to play in every other game of the tour.
2015: Chiefs On 14 February, Williams marked his
2015 Super Rugby return to the Chiefs with a victory over the Blues in the
first round. Two weeks later, he scored his first try of the season against his former club, the Crusaders. On 13 June, after being sidelined for a month with a back injury, Williams returned in the final round of the regular season. The following week, Williams was part of the Chiefs' team that lost to the Highlanders in the quarter-finals. Despite having played only ten of the sixteen regular season games, Williams had the second most offloads, and his nine line-break assists were the highest of any player with ten matches or less. On 8 July, Williams played in New Zealand's first test of the year, in a historic match
against Samoa. The following week he teamed up with Ma'a Nonu in the midfield against Argentina, in the opening match of the
2015 Rugby Championship. On 8 August, Williams played in New Zealand's loss against Australia in the Rugby Championship decider; he also sustained an injury which prevented him from playing in the following weeks' Bledisloe Cup match. On 19 August, Williams was named in coach
Gordon Tietjens' initial squad to represent
New Zealand at the 2016 Summer Olympics in
rugby sevens. Williams said he would commit to rugby sevens full-time following the Rugby World Cup and leading up to the Olympics, in an effort to make the final squad. On 30 August, Williams was named in New Zealand's
31-man squad for the
2015 Rugby World Cup. On 20 September, he played off the bench in New Zealand's opening game victory
against Argentina. Four days later, Williams played in New Zealand's first-ever test match against
Namibia. On 2 October, Williams played in New Zealand's first-ever test match against
Georgia. The following week, he scored a try in New Zealand's final pool stage match
against Tonga. On 17 October, Williams was a part of New Zealand's record-setting quarter-final victory
against France, before playing in the semi-final victory against South Africa. He went on to play in New Zealand's victory against Australia in
the final, before gifting his winner's medal to a 14-year old fan who had been tackled by a security guard during the lap of honour; however, he was presented with a second medal at the
World Rugby Awards the following day. His performance during the tournament, along with those of his midfield partners, was praised by coach
Steve Hansen: "Not only have we lost Ma'a and Conrad we've also lost Sonny. They were the three guys that set the World Cup on fire and allowed us to have a one, two, three punch."
2016: Rugby sevens On 11 January, Williams began training with the
All Blacks Sevens team. However, his introduction to the sport and national team began at the
2015 Dubai Sevens, as a guest of the tournament, where he also witnessed the debut of his sister, Niall, for the New Zealand women's team. His inclusion in the international sevens arena has been "Touted as the biggest gain from the 15-a-side ranks". On 25 January, Williams was named in the squad for the
2016 Wellington Sevens. On 30 January, he marked his international debut
against Russia, scoring a try with his first touch of the ball. He went on to play in the remainder of New Zealand's pool matches. The following day, Williams played in the quarter-final against Kenya, scored a try in the semi-final against England and played in the final's victory against South Africa. After Wellington, he played in the following
2016 Sydney Sevens, including the victory against Australia in the final. He was rested for the subsequent
2016 Las Vegas Sevens and was then ruled out of the
2016 Canada Sevens due to a swollen knee. Williams returned from injury against France in the
2016 Hong Kong Sevens and scored a try in the final pool stage game against Samoa. He went on to play in the quarter-final against Wales, the semi-final against South Africa and the loss against Fiji in the final. The following week he played in the
2016 Singapore Sevens, losing to Samoa in the second-tier Plate final. He went on to play in the
2016 Paris Sevens; however, his tournament was cut short by a knee injury. The following week he played in the
2016 London Sevens, the final tournament of the
World Series, scoring a try against Russia. His tournament was again cut short, by an ankle injury early in the quarter-final loss to the United States, with New Zealand finishing the World Series in third place. On 1 June, Williams announced he had signed a three-year deal (his longest commitment since 2008) to stay with New Zealand rugby until the
2019 Rugby World Cup and would be joining the
Blues in 2017, linking with coach
Tana Umaga for the third time in his rugby career. On 3 July, Williams was
selected to represent New Zealand in
the men's rugby sevens at the 2016 Summer Olympics. His sister, Niall, was also
selected to represent New Zealand in
the women's tournament. On 9 August, in New Zealand's first game of the tournament, against Japan, Williams partially ruptured his Achilles tendon early in the second half. The injury ended Williams' Olympic campaign; New Zealand eventually finished in fifth place.
2017–2019: Blues In 2017 Williams was part of the
Blues super rugby squad. Coming back from injury, his first game for the Blues was in April against the Highlanders, a game where he made headlines for taping over the BNZ logo on his jersey. After a patchy return from injury, Williams looked back in form when the Blues drew with the Chiefs on a rainy Auckland evening. Williams delivered a man of the match performance to help the Blues defeat the British and Irish Lions, 22–16. With time running out and the Lions in the lead, Williams gave an offload to
Ihaia West to score the match-winning try. Williams returned to the All Blacks against Samoa at
Eden Park in a solid performance, where he scored a try in a 78–0 win. A week later, he started at inside centre for the All Blacks in their victory against the British and Irish Lions in the first test. However, a week later in the second test, Williams became the first All Black to be sent off in 50 years after
Colin Meads was sent off in 1967, and was also the first ever to be sent off in New Zealand, for shoulder charging
Anthony Watson to the head. The All Blacks went on to lose the test 24–21. After serving his four-match suspension for his red card, Williams returned for the first Bledisloe Cup match of the year, where he scored a try in the All Blacks' record 54–34 victory. Williams started in all New Zealand's Rugby Championship matches, with the All Blacks winning all six, including a 57–0 victory over South Africa in Auckland. Williams finished the year by starting for the All Blacks three times on the end-of-year tour. In all, Williams played in 13 tests in 2017. After missing a large portion of the
2018 Super Rugby season due to injury, Williams made a return for New Zealand during the
2018 Rugby Championship, having previously played only one test during the year. He went on to play his 50th test for New Zealand, against Australia, during a 37–20 win. Although Williams reached the milestone, he only played one test, against England, during the end-of-season tour due to his continued injury problems. On 28 August, All Blacks Head Coach,
Steve Hansen named Williams as one of 31 players in New Zealand's squad for the
2019 Rugby World Cup, which was Williams' third World Cup. Williams joined teammates,
Sam Whitelock and
Kieran Read in the group of All Blacks to attend three World Cups. Although this was Williams' third World Cup, he lost his place as a regular starter to Chiefs midfielder
Anton Lienert-Brown, being used as a replacement for a pool stage test against eventual Champions, South Africa, as well as two of the playoff matches, against Ireland and England. After New Zealand lost to England 7–19, Williams made a start in his final test for New Zealand in the Bronze Final, a 40–17 win over Wales, which saw the All Blacks claim third place. Williams was one of five players to finish his international career for New Zealand that day, with
Matt Todd,
Ben Smith,
Ryan Crotty and Captain, Kieran Read, all retiring that day, alongside Williams. ==Boxing==