It's believed that Lopez left the team in Los Angeles after playing in Cuba's 7-0 loss to open its Gold Cup campaign.
"The team, as everyone now knows, did not arrive at the Gold Cup with the full delegation and it is true that our No. 4 midfielder Yasmani Lopez abandoned the team on Saturday night," Mederos told reporters, as translated by ESPN FC's Tom Marshall.
"At this point, he is the only player who is not with us," Lopez added. "It is his decision. None of his teammates have anything to do with it. It's his decision. He took it and went through with it."
The 31-year-old Lopez played the entire match against Mexico. He is the latest Cuban athlete to leave the communist country, including the 12 members of the CONCACAF Under-20 Championship squad who defected in November.
Cuba will next face Martinique in Denver on Wednesday before closing out the group stage against Canada on June 23.