The 39-year-old Bulgarian played at Manchester United from 2008 to 2012 and scored 56 goals in 149 appearances.
He won the Premier League thrice, the League Cup twice and the FIFA Club World Cup once in his tenure at the club. He also won the Premier League Golden Boot in the 2010-11 season.
Speaking on Manchester United's current state and its sedentary approach to the transfer market, Berbatov insisted that Ole Gunnar Solskjaer should be looking to strengthen at centre-back.
Berbatov laments Manchester United's defence
He said in an interview to Betfair:
"If we just based it on the first game then Manchester United are miles off the speed of the other top teams in the league, and so I hope it is just down to it being game one. If it becomes a trend, it could be a very long season. I and others have big expectations for United this season.
"They need a centre-half, and probably further recruitment also to be competitive."
Berbatov then elaborated on his point, claiming that the goals Manchester United conceded against Crystal Palace were purely down to bad defending.
"At the end of the day, if Crystal Palace can score three past you, you are in trouble. As I said, if we only judge on this game, United need to buy a whole new squad! But we can't over-react to one game on its own.
"The goals they conceded at the weekend were poor defensive goals." If they don't strengthen up, it will be a long season for them.
"They need someone alongside Harry Maguire, look at how impressive he has been since he came in, and he is now captain.
"They need someone who is fast like Rio Ferdinand was for Nemanja Vidic."
Manchester United may not be in the market for a centre-back but they are reportedly interested in securing the services of left-back Alex Telles from Porto.
The Brazilian defender apparently has his heart set on a move to Manchester United and has agreed on personal terms.
However, United and Porto are still locked in negotiations over the transfer fee.Published 24 Sep 2020, 17:48 IST