West Ham's Reece Oxford has rejected a new deal with the club, Sky sources understand.
It is also understood it would take a bid in excess of £10m for the Hammers to consider selling the 17-year-old, who can play in defence or midfield.
Oxford, who is under contract until 2018, is regarded by West Ham as the brightest prospect to come through the club's academy since Rio Ferdinand.
He made his debut in the 3-0 first leg win of their Europa League first qualifying round tie with Andorran side Lusitanos in July 2015.
Oxford went on to become the youngest Premier League player in the Hammers' history when he started their opening game of the season, a 2-0 win away to Arsenal that set the tone for an impressive campaign for Slaven Bilic's side.
He has since played a further 11 games for the Hammers but his last may have come as a substitute in the 3-0 win over West Brom at the Hawthorns on April 30.