The exciting youngster was named among the substitutes for the clash at Workers' Stadium in Beijing, China, where Lionel Messi wasted no time getting the world champions up and running in the match.
With just two minutes on the clock, Messi received the ball on the edge of the box from Chelsea midfielder Enzo Fernandez and cut inside onto his left foot before bending the ball into the bottom corner.
Argentina controlled proceedings for the majority of the fixture, with substitute German Pezzella doubling their lead in the second half.
Alejandro's big moment came shortly after his side went 2-0 up.