The Brazilian was the club’s only major signing of the summer, arriving from Shakhtar Donetsk for a fee of £52.7m in July.
Fred started Man United’s first three games of the season but, since then, has only managed five starts in all competitions.
Speaking at Carrington on Friday ahead of his side’s trip to Fulham, Mourinho emphasised that he did not feel comfortable using his new signing regularly until the defence tightened up.
“I think Fred, when the team is defensively stronger and doesn’t need in midfield people that is more worried in giving balance to the team than being involved in creation and attacking dynamic, the day we are stronger defensively, I think the horizons for Fred change completely.”
Mourinho clearly took a great deal from those defeats to Brighton and Tottenham Hotspur in August, two games in which Fred started and United conceded three goals, their defence’s soft underbelly often painfully exposed.
Since then, as the defence toiled and changed every week, Mourinho has felt compelled to use Nemanja Matic at the base of midfield, often with either Ander Herrera or Marouane Fellaini as supplements.
For a manager whose primary footballing instincts are to protect and maintain balance, the creative Brazilian midfielder does not appear to be somebody Mourinho trusts at a time when his side is playing poorly and leaking goals.