Los Canaleros will be without their leading forward when they face the United States in Seattle on Tuesday.
The 32-year-old FC Dallas striker is a key component to Panama's attack, with 29 career international goals including two against the USA. He has five goals in 10 games this season for FC Dallas and played 71 minutes for Los Canaleros Friday night against Mexico in a game that ended in a scoreless draw.
There was no definitive word on how long Perez would be out and how his absence may affect his MLS side. FCD plays Texas rival Houston Dynamo in a U.S. Open Cup fourth-round game on Wednesday followed by a crucial Western Conference clash at Portland the following Saturday.
Panama is currently a point behind the USA through four matches in the CONCACAF hexagonal with a record of 1-0-3. In addition to the draw with Mexico, Panama tied Costa Rica and Jamaica and defeated Honduras.