Herrera was voted Manchester United’s Player of the Year last term for his outstanding performances in midfield.
But the Spain international has struggled for form so far this season, leading to talk he could be set for a move away.
Herrera’s Manchester United contract expires at the end of the season and La Liga giants Atletico Madrid have been mooted as potential suitors.
And Spanish outlet Don Balon claims Atletico want to get rid of two players in order to accommodate the Basque midfielder.
Herrera has struggled for consistency ever since joining the Red Devils back in 2014.
He was never quite able to make his mark under Louis van Gaal, who often preferred a midfield combination of Marouane Fellaini and Morgan Schneiderlin instead.
Herrera did seem reborn last term but it appears Mourinho, like his predecessor, harbours doubts about the player.
But Don Balon say Atletico are ready to welcome him with open arms.
It is said Diego Simeone is planning to launch a bid for Herrera in January, despite his contract expiring only months later.
One time United target Nicolas Gaitan is said to be surplus to requirements, with the 29-year-old toiling since arriving from Benfica in the summer of 2016.
And Luciano Vietto is also likely to be shown the exit door.
Meanwhile, another club supposedly interested in Herrera is Barcelona.
And his praise of Barca boss Ernesto Valverde will no doubt fuel talk he could move to Catalonia instead.
“I feel a great admiration for Valverde,” he said.
“He shows that you can be a great coach while being a very great person.”