The 25-year-old, who signed from Shakhtar Donetsk during the January transfer window, has only completed 90 minutes three times in the Premier League this season.

He started the 1-0 Champions League win over Young Boys on Wednesday morning (AEDT) but was an unused substitute in Sunday's 2-2 draw with Southampton, marking the third league game in a row in which he has failed to get off the bench.

Fred's lack of football saw him left out of Tite's last Brazil squad, and he concedes it has been a frustrating few weeks under Jose Mourinho.

"I've played little in the club and it's normal for professor Tite not to be able to evaluate me, even though I've worked hard with him," he said, as quoted by The Daily Mail.

"Of course I was annoyed, but I have to know how to deal with the sadness also, to be able to help me take a step forward. I remain focused on my work and I hope to be back to the selection soon to be able to be in the Copa America.

"The coach Mourinho has chosen not to put me in the team, it's his choice. I still do my job and I can't let it affect my mindset, I cannot let that shake me. I have to be patient.

"It's a bit of a difficult start, I have not been playing so much. I've had a lot of games in Shakhtar, but it's a little bit different here.

"It's normal, a process of adaptation to a different league. Although I've been to Europe before, now I am in a different country and I have to go through a new process of settling in. Today, I see myself much better and I hope that my football will be 100 per cent soon."