In 2011, he switched from Football to Rugby and started aged 17, at Apifo'ou College and represented Tonga U20 at the IRB Junior World Rugby Trophy in 2014, before moving to New Zealand in 2015, initially on a development contract with Tasman. On 20 April 2018, Frizell scored three tries against the in a Super Rugby match at Eden Park. His performances for the Highlanders earned him a call-up for New Zealand's national rugby team, the All Blacks, having been tipped by the media for an unlikely All Black debut. With injury to Vaea Fifita, Frizell made his debut for the All Blacks on 23 June 2018 against France. Frizell started the game at blindside flanker, playing 71 minutes on debut. Frizell had to be taken to the blood bin in the 22nd minute, due to an eye injury, so was temporarily replaced by Highlanders team-mate Jackson Hemopo, who was also on debut for New Zealand. Frizell came back on in the 31st minute and stayed on for the rest of the test, which the All Blacks won 49-14. Frizell went on to start three times for the All Blacks during the 2018 Rugby Championship, in the absence of the injured regular starter, Liam Squire. Frizell was one of the standout performers in the first test against Argentina, on 8 September, playing the full 80 minutes at his homeground in Nelson, scoring his first try for the All Blacks as they won 46-24. Frizell unfortunately failed to make an impact in the final two tests of the competition, including the 32-30 victory over South Africa, 6 October. The All Blacks were drawing 6-6 at halftime, with Frizell subbed off 46 minutes into the test. With Vaea Fifita re-called, Frizell was dropped for the All Blacks' end-of-season tour for 2018. Rookies Gareth Evans, Dillon Hunt and Dalton Papalii were also chosen over Frizell.
2019
After some strong performances in the 2019 Super Rugby season, where he was amongst the highest try-scorers, with six tries, Frizell earned a re-call for New Zealand's 39-man Rugby Championship squad. On 31 July 2019, Frizell and four other players, including Highlanders teammate, Josh Ioane, were dropped from the All Blacks, having performed poorly against South Africa in a 16-16 draw. Frizell was subsequently released back to Tasman for the 2019 Mitre 10 Cup, where he re-established his place as a regular starter for the province. Luke Jacobson's concussion problems continued, which ruled him out of the 2019 Rugby World Cup, to Frizell's benefit. Frizell immediately flew to Japan after Jacobson's injury, to re-join the 31-man All Blacks squad and has played 1 match off the bench versus South Africa and started against Canada and Namibia scoring in the Canada test
