The 17-year-old Spaniard produced a Hollywood strike against Zinedine Zidane's men at the Coliseum in LA to underline his burgeoning potential.
Just as Phil Foden produced a performance to remember against United in Houston, Diaz put down a marker of his own in front of an all-time record football crowd of 93,098 in this stadium.
Diaz said: "It feels really good, but the performance of the team is the important thing.
"It's a friendly but we always want to win against Madrid.
"To play for City now is a big thing for me. It's a big team, I love City, the fans are amazing and the group and the facilities are amazing."