McFarland started playing rugby while attending school at Pesega Church College.[7] He played for the Moamoa Roosters Rugby Club in the local amateur championship, and also represented Moorabbin in the Dewar Shield rugby union competition in Australia from 2016 to 2018.[8] Upon returning to Samoa, he played for the Savai'i Vikings, with whom he contested the Super 9 provincial championship in 2018 and 2019.[9]
In 2019, McFarland was approached by ex-Samoan international rugby player Brian Lima, who was then the head coach of the Samoa Sevens team, to consider switching his focus from basketball to rugby union.[10] McFarland trained with the Samoa 7s, and subsequently signed for Manuma Samoa in the new Global Rapid Rugby competition, which launched in 2020.[11] In the opening round of the inaugural season, he started in the second row against the South China Tigers.[12] However, this was the only match he played in 2020, since the season was immediately interrupted by the COVID-19 pandemic.[13] That same year, he also signed a contract with Major League Rugby expansion team Dallas Jackals for the 2021 season,[14] but he ultimately never joined them, after the franchise opted to delay its entry into the league due to the pandemic.[15]
In August 2021, McFarland agreed a one-year deal to join Saracens in the English Premiership, ahead of the 2021–22 season.[16] He made his competitive debut for the club on 31 October, coming on as a substitute during a league victory against Harlequins.[17] He gradually established himself as a first-team regular, featuring in 27 matches across all competitions that season, including 18 starts and 6 tries, with his playing time split between blindside flanker and lock.[11] He also started in the team's Premiership final defeat to Leicester Tigers.[18]
Ahead of the 2022–23 season, McFarland signed a new long-term contract with Saracens, keeping him at the club until 2026.[19] His performances at the start of the season then saw him named as the Premiership Player of the Month for September 2022.[20] He missed the second half of the season, after suffering an anterior cruciate ligament injury in December 2022.[21] However, he had started all of the team's first 9 matches in Premiership and European competition, scoring 6 tries and helping the team to finish top of the league table, on their way to winning the title.[22]
McFarland received his first call up to the Samoa senior squad in May 2021, from new head coach Seilala Mapusua.[23] He made his debut in July, playing in two uncapped international fixtures against the Māori All Blacks,[1] before earning his first test cap against Tonga in the 2023 Rugby World Cup qualifiers.[24] He then played in all three matches in Samoa's title-winning run at the 2022 Pacific Nations Cup.[25]
Although he missed several months of 2023 while recovering from ACL surgery, McFarland returned to the international stage in the final round of the 2023 Pacific Nations Cup.[11] He was subsequently named in Samoa's 32-player squad for the 2023 Rugby World Cup.[26] McFarland played every minute of his country's four games at the tournament, including a Player of the Match performance against Chile.[27]
In 2024, McFarland was appointed as the new Samoa captain, succeeding Michael Alaalatoa.[28] For his inaugural match as skipper, he led his team to victory over Italy – Samoa's first win against a tier 1 nation for nine years.[29]
