Mata was one of the players of the season in the last Premier League campaign, with pundits and fans baffled at him being reduced to a bit-part player for the Blues so far this season.
That culminated in Saturday's local derby against Fulham, in which Mata failed to even make the bench - prompting fans at Stamford Bridge to hold up signs calling for the player's reinstatement.
It now seems, however, that the only person not calling for Mata's reinstatement is Mata himself.
"He accepts Mourinho has a point, especially when his stats are compared to the likes of Oscar and Eden Hazard," a 'source close to the player' apparently told the Daily Star, referring to the figures backing up the manager's grumbles that the Blues top scorer of 2012-13 is poor at tracking back, tackling and winning 50-50 balls.
Mata was apparently "not impressed" at Mourinho publicly explaining the player's shortcomings in his press conference last week, but he is determined to improve and win his place back.
"He is going to knuckle down and try harder," said a source close to Mata. "If he is given a chance, he will take it."
Mourinho's number two, Steve Holland, hinted at similar feelings behind the scenes in a press conference on Monday.
"There's not a great deal to be said to Juan. He knows the score," he said.
"Jose has his own way. If you look at Ronaldo's three-year period under Jose, he's evolved as an individual.
"He's not just a dribbler, but a top-level match-winner who can run in behind, make runs and threaten the goal.
"That comes with pushing, even pushing the best. Whether it's David, Frank (Lampard), Juan, Fernando (Torres) or Ashley (Cole), he'll be pushing, looking for signs of improvement."