Gurley, the NFL Offensive Rookie of the Year in 2015 and Offensive Player of the Year in 2017, played for the LA Rams from 2015-19 and the Atlanta Falcons in 2020.
Gurley also represented the USA in the 110-metre hurdles at the World Youth Track and Field Championships in 2011.
He put the All Blacks trio through some fieldwork on the outer ground at Snapdragon Park.
He assessed Clarke as a potential linebacker, Williams as a defensive tackle, and Barrett as a safety running back.
The All Blacks thought Gurley would fit nicely into the midfield. Barrett said if he were outside him, he would make sure he got plenty of ball to carry.
The NZR+ Together We Walk series also followed the All Blacks through San Diego, with birthday boys lock Sam Darry and prop Pasilio Tosi featured on local television's KUSI 9 News. Tosi gave one of the news readers an experience of scrummaging.