However, in 14 appearances, the 37-year-old struggled to assert his dominance in a struggling Blues offence and was in no position to stake a claim to another run in the black jersey.
Major League Rugby is a new competition, founded in 2017 with its inaugural season being played in 2018.
The competition features 12 teams, with 11 from the US and one from Canada. The Seattle Seawolves have claimed the title in both seasons played to date.
Nonu will link up with ex-Hurricanes prop Chris Eves and former Waikato No8 Jordan Manihera in San Diego at the commencement of pre-season training this December.
Former Wallabies winger Digby Ioane (Glendale Raptors), Ex-All Blacks Adam Thompson (Utah Warriors) and former French centre Mathieu Bastareaud (Rugby United New York) have also signed on for the 2020 season.