Casemiro has been handed the captain's armband for Manchester United in Wednesday's EFL Cup last-16 contest with Newcastle United at Old Trafford.
The 31-year-old has missed his side's last three games in all competitions, with the midfielder absent against Sheffield United and Manchester City due to an injury that he picked up on international duty.
The Brazilian was also missing against Copenhagen in the Champions League last week, although he would have been unavailable for that contest regardless of his fitness status due to a European suspension.
Casemiro has been declared fit for the EFL Cup game with Newcastle, and with Fernandes on the bench, the 2022 arrival from Real Madrid will skipper the Red Devils.
Following Man United's 3-0 loss to Man City in the Manchester derby, the club's captain Roy Keane said that Fernandes should have the armband taken off him on a permanent basis.
"Today having watched him again I would take the captaincy off him 100%. I know it's a big decision, obviously they changed the captaincy with Maguire, but Fernandes is not captain material," Keane told Sky Sports News.
"He is a talented player no doubt about it. But what I saw today - we've discussed many times before, it was last season at Liverpool - his whinging, his moaning and throwing his arms up in the air constantly.
"It really isn't acceptable. From what we saw today, I'm thinking I would take that off him. You have to start somewhere. We were talking about where do you start [fixing the problems] - the manager, board level.
"I would start with that because the manager is capable of doing that. Fernandes is a brilliant footballer but in terms of captain material he is the opposite to what I would want in a captain."
Fernandes was appointed Man United's new captain over the summer, with Harry Maguire removed from the role due to his struggles in breaking into the side last season.
Casemiro's defensive performances for the Red Devils have been called into question this season, but he has scored four times and registered one assist in 11 appearances.
Man United against Newcastle is a repeat of last season's EFL Cup final, and Casemiro told United Review that he is expecting "a great game".
"We've got to really go for it in the game and be really focused. It'll be a great game for both teams. We're really excited for this game because Manchester United vs. Newcastle United is a huge fixture, and this time around it'll be no different," said the South American.
Man United will then switch their attention back to league affairs after the clash with Eddie Howe's side, heading to London to take on Fulham in Saturday's early start.
