Atlanta United suffered a 3-1 loss to Herediano in the opening leg of their CONCACAF Champions League tie in Frank de Boer's first competitive game in charge.
De Boer was appointed coach of the MLS champions in December, replacing Gerardo Martino, who took charge of Mexico.
But the Dutchman tasted defeat in his first competitive outing, as Atlanta went down to begin the last-16 tie in Costa Rica.
The visitors were punished in just the seventh minute, Jose Guillermo Ortiz pouncing on a poor headed backpass to lob goalkeeper Brad Guzan.
Herediano doubled their lead 11 minutes before half-time, Randall Azofeifa getting in behind to put away a pass from Ortiz.
However, Atlanta managed to pull one back through Julian Gressel, only for the hosts to restore their two-goal advantage early in the second half when Oscar Granados tucked away an Azofeifa set-piece.
It leaves Herediano well-placed to reach the quarter-finals ahead of the second leg on February 28.
There was better news for another MLS club as Sporting Kansas City cruised to a 3-0 home win over Toluca.
Krisztian Nemeth, Gerso Fernandes and Ilie struck to give Sporting a first-leg victory.