Former Manchester United defender Rio Ferdinand has urged the Red Devils to go all out for Erling Braut Haaland or Kylian Mbappe in the summer transfer window.
With Mbappe yet to agree an extension over a new deal at Paris Saint-Germain past 2022, the World Cup-winning Frenchman is being linked with a big-money move to another top club on the continent.
Borussia Dortmund could also be forced to part ways with Man United-linked Haaland if they fail to qualify for the Champions League, and Ferdinand believes that United need to "move heaven and earth" to land one of Europe's top prospects if they want to challenge for the title.
Speaking to the FIVE YouTube channel, Ferdinand said: "I still see room for improvement, we definitely need to buy a centre-back, a commanding centre-back with pace, please!
"I think [Edinson] Cavani, yes, he's a good stopgap but [we need] a centre forward. If people like Erling Haaland or Kylian Mbappe are available, you can't allow them to go somewhere else and you need to move heaven and earth to get them here.
"Manchester United are used to having superstars and those boys would change the narrative at this football club, that's how good they are.
"There's room for improvement and opportunity to improve this squad, there's players out there available, it seems. We need to be in the mix."