Many clubs are seeking to buy the Milan youngster Gianluigi Donnarumma.
He is regarded as the top goalkeeping prospect in the world.
But Milan are not in a selling mood, per their sporting director Massimiliano Mirabelli.
"Apart from his mistake, he played a great game tonight," Mirabelli told reporters after Milan lost to Arsenal in the Europa League.
"We want him to stay with us for a long time. He's a gem of ours and the whole of Italy, and we're keeping a tight grip on him."