The report claims Mourinho is adamant Mata will stay at the club, following speculation PSG could be set to launch a €41m bid for the Spaniard in the January transfer window.
But the Chelsea boss is not willing to consider any offers, as he sees the battle for the playmaker spot in the Stamford Bridge midfield as a straight fight between Oscar and Mata.
At the moment, Oscar holds the advantage. The Brazilian international has made nine Premier League appearances so far this season, scoring four goals while Mata has just five appearances and no goals.
But Mata impressed against Arsenal in the Capital One Cup this week, and is pushing for a recall to the starting eleven in the Premier League.
He was the subject of a £30m bid from PSG over the summer - one that Chelsea turned down, but recent reports claimed the big-spending French club were poised to return in the winter window.
Many believe Mourinho has favoured Oscar because of his work rate, willingness to muck in with defensive duties and his pace compared to Mata's more technical approach.
But the two-time Chelsea player of the year remains a fan favourite at Stamford Bridge, and the report claims he's still very much part of Mourinho's plans for the season.