The Daily Star says Blues boss Jose Mourinho made it clear on the eve of the Fulham game that despite Spanish star Mata being Chelsea's top scorer last season with 20 goals, he was unhappy with his contribution in other areas, like tracking back, tackling and winning 50-50 balls.
And Mata - having seen the statistics to back up Mourinho's complaints - has agreed his coach has a point.
It is understood that although Mata was not impressed at how Mourinho made his points about his shortcomings so publicly, he is ready to adapt his game.
"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. He accepts Mourinho has a point, especially when his stats are compared to the likes of Oscar and Edin Hazard."