Gary Neville called Bruno Fernandez and Harry Maguire “irreplaceable” for Manchester United.
And he warned Ole Gunnar Solskjaer that he could not afford a vacation for any of the men during the current club schedule.
United have reserved their place in the last four Carabao Cups with a 2-0 win over Everton on Wednesday night.
Edinson Cavani and deputy Anthony Martial scored late goals for the Red Devils at Goodison Park as the much-changed side booked a semi-final showdown with Manchester City next month.
Of the team that smashed Leeds United in the Premier League on Sunday, Solskjaer have made nine changes, with only the club captain and the Portuguese mascot retaining places in the starting line-up.
For the United Neville legend, that says enough.
Speaking on his Sky Sports Podcast, Neville said: “They are two players that I consider to be irreplaceable.
“Fernandez is irreplaceable, they are far without him. He is an important part of the puzzle.
“Maguire, I think you’d know he wasn’t there. I think they would miss him very much.
“I know some people say that he is not the best defender in the league, that he has not done great since he came for 80 million pounds, but he has a great presence in the heart of the defense.
“He is good in the ball, he is calm and he is good in the air.
“He doesn’t make a lot of mistakes, sometimes they catch him, but he is a good center shot, a really good center forward and a great presence in that team.
“He and Fernandes, I’m not sure I can [rest them] at the moment, because Ole, unfortunately, does not have the luxury of losing the game. “
United will face Leicester in the early start of the Premier League on Boxing Day, starting the game in third place, one point behind their opponents sitting second – albeit with a game in hand.
On December 29, they host the Wolves, on the eve of the New Year’s meeting with Aston Villa, also at Old Trafford, who suddenly appeared as potential candidates for the title in the Premier League.
Can Man Utd win the Premier League or are the top four the pinnacle of their aspirations this season? Have your say here.
* Sign up to email Mirror Football here for the latest news and gossip