Flick opens his Barcelona tenure with win over Manchester City
Toni Fernandez, who signed with Barca earlier this month after turning 16, flicked in a left-footed shot past reserve City goalkeeper Stefan Ortega to give the German manager's side a 4-1 win on penalties.
Barcelona kicked off their US tour in the pre-season contest against the four-time reigning Premier League champions, guided by former Barcelona player and coach Pep Guardiola.
A sellout crowd of 63,237 spectators were unhappy early as a storm delayed the start by 80 minutes, but were delighted with a strong early pace, before both teams gave reserve players abundant time on the pitch.
Barcelona jumped ahead 3-0 on penalty kicks thanks to a left-footed shot by Alejandro Balde before Amar Ahmed kept City in it by beating reserve Barca goalkeeper Ander Astralaga, setting the stage for the teen newcomer's heroics.
Pau Victor had opened the scoring in open play for Barcelona in the 24th minute, taking a quick through ball pass from Marc Casado and firing a right-footed blast from the right side into the goal.
Nico O'Riley answered for Manchester City in the 39th minute, firing in a left-footed shot from the left side off a pass from Josko Gvardiol, the Croatian international making his first US tour start.
Pablo Torre's goal in the second minute of first-half stoppage time gave Barcelona a 2-1 half-time lead.
The 21-year-old Spanish midfielder took a centering pass from Gerard Martin at the left wing, nudged the ball to his right, then blasted a right-footed shot past Brazilian goalkeeper Ederson and inside the left post.
Jack Grealish equalized for City in the 60th minute off an impressive fast break.
Croatian international Mateo Kovacic, making his first start on City's US tour, gathered a loose ball just beyond the City box, split two defenders and raced upfield with the ball before passing to English left winger Grealish, who outraced a defender and finished with an outstanding left-footed shot from a steep angle high into the goal.
Barcelona will continue their US tour with pre-season matches against Real Madrid and AC Milan.
City, who lost earlier US matches to Celtic and AC Milan, will close the US tour by facing Chelsea on Saturday at Columbus, Ohio.