The 20-year-old has been linked with a move away from Doria after impressing for the club last season.
“Poli is of interest to both Milan clubs,” Samp director general Sergio Gasparin noted. “He has the potential to become the best Italian midfielder in the game.
“We’re just happy that he is with us for now even though we know that he is destined to play on some of the most important stages in the European game.”
