The Mexico U-23 team stumbled in their first game of their trip to Portugal, falling 2-1 to Japan in friendly on Friday.
The young El Tri side is set to defend their gold medal triumph in this summer's 2016 Rio Olympics.
Only a minute into the game, Shoya Nakayima's deflected shot beat Gibran Lajud to put the Asian champions in front.
Shortly past the half-hour mark, Japan doubled their lead when a backheel play from Yuya Kubo finished with Takumi Minamino firing home Japan's second.
After going into the break with a two-goal lead, Japan were content to allow Mexico possession and lock down their defense.