Gary Neville says Manchester United need to bring in at least two top central midfielders in the summer transfer window and has laid out the profile of signings his former club require.
United moved one step closer to Champions League qualification with Sunday's 3-1 win over Aston Villa, cementing their place in third, and Neville warned they need reinforcements to cope with the tougher fixture schedule.
Michael Carrick has relied on a midfield pair of Kobbie Mainoo and Casemiro but the Brazilian is set to leave at the end of the season and alternative options are slim in the current squad.
"The centre of midfield is a problem," Neville said on his Your Site podcast. "Kobbie Mainoo and Casemiro are doing a great job right now for Michael Carrick.
"However, every Manchester United fan in this stadium know that is going to be nowhere near enough when they start playing in the Champions League next season.
"It is more than likely they will [qualify] and when they play a bit further in the FA Cup and Carabao Cup and they are playing in the Champions League they are going to need three or four really good midfield players.
"At the moment you've got Mainoo, a midfield player you can buy into, but you can't really look at any of the others and think that is going to work.
"Casemiro is leaving and I think Manuel Ugarte will leave. They need two really good central midfield players. Probably one that's more positional, like a Michael Carrick-type, and one that's more of a destroyer.
"The back needs looking at but midfield would be the real focus in the summer transfer window."
United's priority this summer transfer window is signing at least one - and potentially two - top central midfielders.
Nottingham Forest's Elliot Anderson, Crystal Palace's Adam Wharton and Brighton's Carlos Baleba and Wolves' Joao Gomes are among the players on their shortlist.
United are also looking at younger prospects such as Lille's Ayyoub Bouaddi and Olympiakos' Christos Mouzakitis.
United prioritised bolstering their attack over the summer, spending more than £200m on Matheus Cunha, Bryan Mbeumo and Benjamin Sesko, and it is clear that midfield is the next area of focus.
However, United's defence is not without issue. Matthijs de Ligt and Lisandro Martinez, who have been consistent starters when fit, continue to be plagued with injury problems.
Harry Maguire is also out of contract this summer and a decision needs to be made on his future.
Neville believes those fitness concerns are an issue and has questioned if left-back Luke Shaw would be able to cope playing week in, week out if United qualify for the Champions League.
"It might then be the summer after [this one] when they finally get round to new centre-backs because they have got a problem.
"The problem at centre-back actually at the moment is that De Ligt and Martinez arguably - with Maguire - their two best centre-backs, can't get on the pitch and it's a real problem.
"Shaw is playing every week and he's more than good enough to play out here every week, let's be clear, but how long is that going to last for? Can he do that next season, the season after and the season after?
"If he can, Shaw's your left-back, no problem, because I don't think you'll find a better left-back.
"[Coping with Champions League schedule] is the issue when every three days comes. United are going to need someone at left-back to cope without him.
"Is he going to break down if he's playing 55-60 games rather than 35-40 and that's the question that will need asking next season.
"There is a doubt there but not on the quality of the left-back. It's on the actual resilience and robustness of him when he plays every three or four days."
Neville says United are still right to let Casemiro go at the end of the season despite the midfielder's renaissance this season.
"Obviously, Manchester United got him at the latter part of his career. What he was is an exceptional central midfield player who played in one of the most dominant midfields that you'll ever see at Real Madrid," he said on The Gary Neville Podcast.
"But it's right that United do let him go, and it's right that he does leave United. This is like a cameo at the end of his career. Almost like a swansong where he's probably loving every minute, and you can see it.
"He's kissing his badge to the fans. The fans absolutely love him, and it's right that he does leave at the end of the season.
"His legs at times have let him down. What I would say is there's a period in the middle of his four-year contract where he looks heavier in his body and I don't know what happened there.
"Whether it's the training, whether it's something that's happened with him or whatever, I don't know. But he looks fitter, he looks leaner, he looks freer and look, he's doing a great job."
