The trio of United young stars have been deemed surplus to requirements according to a report in the Telegraph.
Wilson and Blackett have been omitted from the club’s tour of China and while Keane has been included, he will also be allowed to leave this summer.
Mourinho has already made a number of key additions to the squad and is happy to let fringe players as well as a number of recognisable faces leave in the coming weeks.
Zlatan Ibrahimovic, defender Eric Bailly, and attacking midfielder Henrikh Mkhitaryan have all arrived in recent weeks.
Wilson and Blackett are both England Under 21 internationals and have made starts, but failed to fully established themselves in the team, and both spent most of last season out on loan while Keane has struggled with injuries.