Luke Shaw links up with Manchester United squad after clear-the-air talks
The full-back was left out of United's 18-man squad to face West Brom on Saturday and afterwards United boss Mourinho blasted the 21-year-old's fitness and attitude.
Having been made aware of the criticism on Sunday evening, Press Association Sport understands that Shaw held a meeting the following day with Mourinho to discuss those comments at the Aon Training Complex.
T he talks appear to have led to a breakthrough after the England defender was seen checking into United's team hotel ahead of Tuesday night's Premier League clash.
Record signing Paul Pogba, who has missed United's last two games with a hamstring complaint, was also present.
Shaw's future at Old Trafford appeared bleak when Mourinho said he was "a long way behind" his team-mates.
Mourinho added: "I cannot compare the way he trains, the way he commits, the focus, the ambition."
That prompted former United full-back Phil Neville to tell Shaw to "pull his finger out" to save his Manchester United career.
Neville felt Mourinho was simply trying to give the player a "jolt" - a theory which will look increasingly likely should he be involved against Everton.
"If I was Luke Shaw, I wouldn't be looking to get out of Manchester United," Neville told Press Association Sport on Monday.
"I'd be looking at that situation thinking that on Saturday (Mourinho) played Ashley Young at left-back, that he has been playing Matteo Darmian at left-back, Marcos Rojo, Daley Blind. These are players who are not out-and-out left-backs.
"So rather than thinking 'the manager doesn't rate me', I'd be thinking 'I have to pull my finger out here' and think the opportunity in front of me is absolutely huge, to be the number one left-back at one of the biggest clubs in the world.
"Something has to change for Luke Shaw, because someone with that ability has got to be England and Man United's number one left-back, and if he's not, then there is something fundamentally wrong.
"The comments coming from Jose Mourinho suggest there may be an attitude problem or a professionalism problem, and if that is the case, this could be the kick up the backside he needs.
"He needs to probably take a long hard look at himself and realise the opportunity that is in front of him.
"In life, you only get one opportunity at a club like Manchester United, and if you don't grasp that opportunity, you end up being sold and going maybe back to Southampton, thinking 'should have, would have, could have'."
Shaw has made just two United appearances in the last four months after an injury-ravaged 2016 and has been publicly criticised by Mourinho on several occasions.
The England left-back's last match came a month ago against Bournemouth, when Press Association Sport understands Mourinho was angered by Shaw speaking to an opposition player at half-time.
Relations have been frosty ever since, with Shaw out in the cold despite doing extra sessions at home on top of United training, but Monday's meeting with the manager, and subsequent invite to join up with the squad, could prove a turning point.