The English side recently forked out €39 million to secure the services of midfielder Donny van de Beek from Eredivisie champions Ajax Amsterdam.
Manchester United also have the likes of Paul Pogba, Nemanja Matic, Bruno Fernandes and Scott McTominay to choose from in midfield.
The Red Devils are said to be willing to sign Borussia Dortmund wonderkid Jadon Sancho but Berbatov believes the Manchester-based team are well stocked in midfield and should be looking to add a center-back, who possesses a different features compared to Maguire, to their ranks.
“I think in defense, a center-back is something that they need to look for,” Football365 quoted Berbatov.
“If they are going to buy someone or not we are going to see, but I think that is where they need to strengthen. Everything else at the moment looks balanced.
“For me they need someone who can accommodate Harry Maguire. Harry is more of a guy for getting the ball out of the defense and giving it to the midfield, so maybe someone who is different to that but also strong.
“They need to copy the Rio [Ferdinand] and [Nemanja] Vidic partnership from the past.”
Berbatov played for Manchester United between 2008 and 2012 where he scored 48 Premier League goals in 108 appearances.
He also won two league titles, one League Cup and one FIFA Club World Cup during his four-year stay at Old Trafford.
