Born in the town of Masterton, New Zealand, Shields attended Taita College in the suburb of Lower Hutt where he played first XV rugby and served as deputy head boy. After finishing high school, he began playing for Petone in Wellington's local club rugby competition while also captaining at under-20 level.
Senior career
Shields made his provincial debut aged just 19 in 2010. Taking advantage of injuries to established players Rodney So'oialo and Serge Lilo, he played in a 52-23 victory away to. That was to be his only appearance during the season, however the following year, he became much more of a regular, featuring 10 times and scoring his first 2 provincial tries as the Lions finished a disappointing 6th on the Premiership log. After missing the entire 2012 ITM Cup due to injury, he returned fully charged in 2013 and played 11 of Wellington's 12 games in a season which saw them finish top of the Premiership log before being defeated 29-13 at home by in the playoff final. 2014 would be a year of turmoil for the Lions as they came 7th and last in the Premiership, recording just 1 win in 10 games. Shields captained the side and was named as Wellington's Player of the Year for his efforts. The Lions failed to gain promotion to the Premiership at the first time of asking, finishing 2nd, behind on the Championship log before being defeated by the same opposition in the playoff final, narrowly going down 26-25. Injury restricted Shields to just 6 matches in 2015 where he scored a try and picked up a yellow card. 2016 saw Wellington once again come to close to earning promotion but yet again falling just short. After another 2nd place log finish, this time behind, they were upset at home by, 40-37 in the playoff semi-finals. Shield played 9 of 11 games during the campaign. It was announced on 19 November 2017 that he will join Wasps in 2018.
With just a little over a season's experience of provincial rugby under his belt, Shields was signed to a Super Rugby contract with the ahead of the 2012 season. Faced with stiff competition for a place in the starting line up from the likes of Jack Lam, Faifili Levave, Karl Lowe and Victor Vito, he acquitted himself well and went on to play 13 times during his debut season of Super Rugby, with 10 of these appearances coming from the replacements bench. He enjoyed a breakout year in 2013, playing in all 16 of the Hurricanes games, including 13 starts and 3 tries before a knee injury hindered him in 2014, restricting him to only 6 matches. The Hurricanes were one of Super Rugby's form teams through 2015 and 2016, finishing as runner-up in 2015 following a 21-14 home defeat to the, before finally getting their hands on the trophy at the end of the 2016 season after a 20-3 victory over the in the final. Shields featured heavily in both campaigns, playing 18 times in 2015 and 16 times in 2016 as well as contributing 2 tries in each season. On 27 June 2017, Shields captained the Hurricanes to a historic draw against the touring British and Irish Lions side. Shields was replaced by Reed Prinsep in the 56th minute, with the Hurricanes finishing the game at 31-31. Shields was named as captain of the Hurricanes for the 2018 season despite his upcoming departure, with regular captain Dane Coles ruled out for the season with a torn ACL.
International
Shields was a New Zealand Under-17 representative in 2008 before being a member of the New Zealand Under-20 side which won the 2011 IRB Junior World Championship in Italy, scoring 1 try in 5 matches at the tournament. He has been named in All Blacks training squads in 2012 and 2016, but has not gone on to make his senior international debut. On 5 November 2016, he featured for the Barbarians in their 31-31 draw against at Wembley Stadium. He played the entire 80 minutes in the number 6 jersey in a side containing his Hurricanes teammates, Reggie Goodes and Michael Fatialofa. On 9 June 2018, he made his debut for England, coming on as a replacement in England's narrow defeat against South Africa at Ellis Park. He was then named as a starter for the second test against South Africa the following week. Having established his place as a regular starter for England throughout the 2019 Six Nations Championship, Shields missed selection for the 2019 Rugby World Cup, having been ruled out of contention for the competition through injury. Uncapped player, Lewis Ludlam, was called in as a replacement for Shields during warmup fixtures.
