Blackadder missed the 2020 Mitre 10 Cup with injury as the Mako went on to win their second premiership title in a row.
Blackadder played every minute of the Crusaders 24–13 win over the Chiefs in the 2021 Super Rugby Aotearoa final as the side won their fifth title in a row.
After an outstanding 2021 Super Rugby season Blackadder was named in the All Blacks squad to play Tonga and Fiji in the July Steinlager Series.
[6] He was named in the travelling squad for the 2021 Rugby Championship and the end of year tour of Europe.
Blackadder was not selected in the All Blacks World Cup squad for the 2023 competition, however was called in as injury cover.