Barcelona and Real Madrid are monitoring JJ Gabriel's stand-off with Manchester United, sources have told ESPN. The 15-year-old and his representatives have stunned Old Trafford bosses by demanding to leave. United will not cancel his contract and he cannot be de-registered, but his stance opens the door to a departure next summer.

He becomes eligible to sign scholarship forms after his 16th birthday on Oct. 6. Spanish giants Barcelona and Real Madrid have both been alerted, with Real Madrid's plan involving their B-team. Gabriel can move to a European side because he holds an Irish passport.

Premier League clubs including Manchester City and Chelsea are also watching developments, though one source close to a prominent English club believes Gabriel will eventually agree a way back at United. United bosses remain hopeful the situation can be rectified and insist they do not know the exact reasons behind his desire to leave. Gabriel was in line to be part of Michael Carrick's squad for the Carabao Cup tie against Brighton, which would have made him United's youngest ever player, but is now set to be left out after missing training this week.