The Toon, who beat the drop on the final day of last season, completed the signing of the 20-year-old Anderlecht star earlier today.
Mitrovic - who scored 23 goals last season - caught the eyes of a number of teams with a string of impressive performances, including Newcastle's Premier League rivals Manchester United.
However, the Serbia hitman was on the Special One's radar long before Newcastle and United became interested in acquiring his services.
Speaking after Serbia's clash with Croatia two years ago, the former Real Madrid and Inter Milan coach hailed the new Toon striker and backed him to become a 'European star'.
“Mitrovic was the best player on the pitch,” said Mourinho.
“He managed to keep the ball well and that was the key.
"That boy has everything to be a European star.”
Mourinho's comments regarding Mitrovic will certainly fuel speculation that the Portuguese will make a move for the former Anderlecht ace.
Starsport revealed last week that the Blues chief was interested in snapping up the prolific striker, who is allegedly keen on a move to Stamford Bridge in the future.
