Singapore - New-look Arsenal left out controversy-hit Mesut Ozil but still impressed before they were edged 3-1 on penalties by Europa League champions Atletico Madrid in a friendly on Thursday.
Ozil, who caused a furore when he quit German national duty claiming racism, was rested after his World Cup exertions as 17-year-old midfielder Emile Smith Rowe took centre-stage in Singapore.
After Luciano Vietto's opener for Atletico against the run of play, teenager Smith Rowe hit a dazzling equaliser - his first senior goal - in front of new boss Unai Emery as it finished 1-1 after normal time.
Under International Champions Cup rules, the game went straight to penalties where substitute Atletico goalkeeper Antonio Adan starred, saving three before coolly slotting the winner himself.
Both sides started with unfamiliar line-ups but Arsenal were the dominant force in the first half before they were hit with a sucker-punch four minutes from the break.
In a rare Atletico foray forward, Angel Correa crossed from the byline to his fellow Argentine Vietto, whose header looped past new Arsenal goalkeeper Bernd Leno.
The German, starting ahead of Petr Cech in goal, otherwise had little to do as Arsenal, employing Emery's trademark high press, kept Atletico in their own half.
French forward Alexandre Lacazette was denied from close range on three occasions, including a full-length save by Atletico's Jan Oblak after good work from Smith Rowe.
But Arsenal struck two minutes into the second half when Smith Rowe curled the equaliser into the top corner from the edge of the box, before being mobbed by his team-mates.
Mass substitutions in the last half-hour made for a disjointed finale before the penalty shoot-out.
Arsenal, rebuilding under Emery after Arsene Wenger's 22-year reign, are hoping for silverware this season and a return to the Champions League, while Atletico finished second in La Liga behind Barcelona.