Jose Mourinho may have spent around £150 million last summer but it seems the Portuguese manager needs to spend a lot more if he is to return the Red Devils to the summit of English football.

Despite the arrivals of Paul Pogba (£89m), Eric Bailly (£30m), Henrikh Mkhitaryan (£26m) and Zlatan Ibrahimovic (free), United are still well off the pace in terms of the title race this season.

Mourinho’s side have remained sixth in the Premier League for the majority of the campaign and are 12 points adrift of Chelsea at the top of the table.

And it seems Mourinho will delve into the transfer market once again at the end of the season as he aims to win United’s first league title since 2013.

Despite there still being months until the window opens, there has been plenty of players linked with a summer move to Old Trafford.

At the top of that list is Atletico Madrid’s Antoine Griezmann.

The Frenchman has been heavily linked with a move to the Theatre of Dreams in a deal that could surpass the £89m spent on Pogba.

And, after watching Griezmann score his 17th goal in 34 Atleti matches during their Champions League clash against Bayer Leverkusen, one United legend believes he would be a fantastic signing.

Keane is 'shocked' by Griezmann

That man is Roy Keane - a man that is notoriously hard to please. However, he admits he is “really shocked” by his performance levels and believes he would be great for United.

"He's been fantastic," Keane told ITV.

"I've been really shocked over the level he's played at over the last two years, he's been fantastic.

"We're seeing the goals now, on a regular basis, in all the big games, international level and big Champions League nights.

"We can talk all day about the poor defending, it's really poor and it was so open on the night, but it's a great finish from a really top player.

"He's obviously been linked with United, what a player he'd be for United."

While Keane can appreciate Griezmann’s talents right now, he probably wasn’t singing his praises during last summer. That’s because the forward’s two goals at Euro 2016 knocked out the Republic of Ireland - with Keane being assistant manager for his native country.

But Keane isn’t the only former player to urge Mourinho to splash out on the 25-year-old.

Scholes on Griezmann

Keane’s former midfield partner, Paul Scholes, also believes they do all they can to bring him to the club if the opportunity arises.

"If Griezmann is within reach, why wouldn't we take advantage and try to sign him, especially if our youngsters aren't at the level we need?" Scholes said.

"At United, there is always a lot of pressure to win the Premier League and the Champions League."