Herrera has struggled for Manchester United this season with the Spain international stuck behind the likes of Paul Pogba, Nemanja Matic and Scott McTominay in Mourinho’s pecking order.
The former Athletic Bilbao star was in sensational form last term, helping the club win the EFL Cup and Europa League, but game time is hard to come by at present.
And the Daily Mail say Manchester United are not playing Herrera because his relationship with Mourinho has been damaged following an incident that happened last season.
The club were challenging for the Europa League in April last year.
It was their only chance of securing Champions League football for this season with their Premier League campaign, at the time, in ruins.
Herrera supposedly invited a friend with close links to Celta Vigo, their semi-finals opponent, to the club’s Carrington training complex.
And Mourinho, the Daily Mail say, was furious about the incident.
He reportedly took Herrera into his office and laid down the law to the 28-year-old.
And what has happened since suggests their relationship is damaged beyond control.
Herrera has made just eight league starts all season.
And, with Barcelona reportedly keen to snap him up, a parting of the ways could be in the offing come the summer.
Speaking in September, however, Herrera admitted he was fine with playing when called upon.
“I am always ready to play,” Herrera said. “I always say the same.
“I am a team player and when the manager needs me, I will be there and that’s it. In football, there are no surprises.”