That’s the view of United legend Gary Neville, who has made the claim despite his former side progressing to the quarter-finals of the Champions League.
Manchester United were 2-0 down to PSG heading to the second leg in Paris on Wednesday.
But a brace from Romelu Lukaku and a last-gasp penalty from Marcus Rashford put United through on away goals.
Ole Gunnar Solskjaer’s side travelled to the French capital with a threadbare squad, full of young stars.
And Neville believes the Old Trafford outfit need to bring five players to the club in the summer and has outlined who they should be.
The former right-back told beIN Sports: “Manchester United need two centre-backs. I genuinely believe that.
“When you talk about United winning the Premier League title or trying to get to a Champions League final, you need top centre backs.
“They need two new centre backs and a right back. That’s a minimum I think for the summer. They’ve looked at doing that in the past and they need to do it this year.
“The manager needs a new back four, there’s no doubt.
“They need someone with authority. You watch Virgil van Dijk or Thiago Silva, they’re world-class centre backs and United need someone like that.
“I would say three defenders, one midfielder and one forward, because of the form of Alexis Sanchez.
“Unless he completely changes what he’s doing in the next few months, United need another forward.
“I’d say they need five additions to the squad. Then the squad would be in good shape and could challenge.”
Manchester United face another crunch clash this weekend as they look for a place in the Premier League top four.
The Red Devils travel to Arsenal on Sunday (4.30pm).