Jose Mourinho has promised Fred's "horizons will change completely" when Manchester United are better defensively.
Fred voiced his frustration that a lack of playing time at United had cost him his place in the Brazil squad last week.
He has made just six Premier League appearances since his £52m move from Shakhtar Donetsk in the summer and was not even among the substitutes for the 2-2 draw with Arsenal on Wednesday.
Ander Herrera, Nemanja Matic and Jesse Lingard were preferred in a midfield without Paul Pogba, with Mourinho saying he had found his 'mad dogs' in the side.
Fred is adapting to English football "step by step", according to Mourinho, and is paying the price for United's collective weaknesses.
"When the team is defensively stronger and does not need in midfield people that are more about giving some balance to the team than being involved in creating and attacking dynamics - the day we are stronger defensively, I think the horizons for Fred change completely," said Mourinho.
"You have also other players in other clubs that needed time. You have some of them that play even less than what Fred is playing."
Mourinho was waiting for Friday's training session to assess the fitness of Chis Smalling, Phil Jones, Anthony Martial and Eric Bailly - while Victor Lindelof and Alexis Sanchez are "not worth speaking about".
But the United boss admitted "we need answers" ahead of playing Fulham on Saturday.
"For sure we are not going to play with players in the maximum of their potential," Mourinho said.
"But players that will make themselves available for the team like Smalling did in the last match, like Jones did against Southampton, will play."