Kane Ferdinand will miss Southend's clash at Stockport after the Republic of Ireland Under-19s refused to release him.
Shrimpers boss Paul Sturrock had hoped the teenage midfielder, who signed his first professional contract with the Essex club on Monday, would be allowed to face the Hatters in League Two on Saturday.
But the Irish Football Association have insisted Ferdinand must travel with the Republic squad for their game in Cyprus this weekend.
Sturrock told the club's official website: "We're obviously disappointed to be without Kane for Saturday.
"Since coming back from injury he has done well, so it is obviously a blow to be without him.
"When a Football Association requests you release a player you don't have much say in the matter, but we were hopeful they could see the benefits of young Kane playing first-team football."