Manchester City have officially completed the signing of Ruben Dias from Benfica.

The Portuguese star becomes the latest big-money defensive acquisition of the Pep Guardiola era, joining the Citizens for a fee of around £61.20m

That price tag makes the 23-year-old the third most expensive Premier League defender of all time, behind only Virgil van Dijk and Harry Maguire.

Will Dias' enormous price tag hinder his performances in the English top-flight? We don't know as of yet, but we've decided to have a look at whether spending big bucks on defenders is actually worth it.

Below, we've provided the 15 most expensive defenders in Premier League history and graded them all out of 10.

Dias in Man City's shirt

Given that Dias, Nathan Ake and Ben Chilwell have barely played for City and Chelsea as of yet, we've decided to be fair and omit them from the list.

Fees sourced from Transfermarkt.

Maguire with Man Utd

Harry Maguire to Man Utd | £78.30m

Grade | 6/10

Maguire's debut season at United was far from the worst, but the club captain's performances have not yet been befitting of the world's most expensive defender.

Virgil van Dijk to Liverpool | £76.19m

Grade | 10/10

No one ever thought spending £76.19m on a centre-back would turn out to look like a bargain, but that's how good Van Dijk has been. Arguably the Premier League's greatest ever defender.

Joao Cancelo to Man City | £58.50m

Grade | 5/10

There are small signs that Cancelo is starting to find his feet at City but up to now, the signing of the Portuguese has been a pretty poor one - especially given he's the most expensive full-back of all time.

Cancelo in action

Aymeric Laporte to Man City | £58.50m

Grade | 9/10

City sometimes pull the rabbit out the hat when it comes to signing defenders. Laporte is the definition of world-class and like Van Dijk, his enormous fee looks like a bargain these days.

Benjamin Mendy to Man City | £51.75m

Grade | 5/10

When fully fit, Mendy is the perfect left-back for Guardiola's system. Sadly, the Frenchman has been unable to string a prolonged run of games together on English soil and therefore we cannot grade him higher than 5/10.

John Stones to Man City | £50.04m

Grade | 6/10

We're giving Stones 6/10 purely down to his impressive performances during City's 2017/18 title-winning campaign. But these days, the Englishman looks like a £20m player at best.

Stones warms up with City

Aaron Wan-Bissaka to Man Utd | £49.50m

Grade | 6/10

Brilliant in defence but suspect going forward, Wan-Bissaka is far from the finished article at United. His performances in big games during the 2019/20 season are why we've decided to grade him just above average.

Kyle Walker to Man City | £47.43m

Grade | 9/10

One of the best right-backs in Premier League history and a signing that transformed City as a team. It's not a coincidence that Guardiola's side stormed to the title in record-breaking style after the former Tottenham man's arrival in the summer of 2017.

Rio Ferdinand to Man Utd | £41.40m

Grade | 10/10

It's amazing to think United splashed over £40m on Ferdinand in the summer of 2002, but Sir Alex Ferguson's expensive gamble paid off - to say the least. Just the 14 major trophies for Ferdinand with the Red Devils...

Man Utd legend Ferdinand

Eliaquim Mangala to Man City | £40.50m

Grade | 1/10

Far and away the worst signing on this list. Despite costing over £40m, Mangala's performances in the Premier League were that of a Championship player - at best.

Nicolas Otamendi to Man City | £40.05m

Grade | 5/10

Like Stones, we're giving Otamendi a slight boost due to his performances for City in 2017/18. Had it not been for that campaign, the Argentine would be far closer to Mangala's grade.

Shkodran Mustafi to Arsenal | £36.90m

Grade | 3/10

Mustafi's Arsenal career started promisingly, but things quickly turned sour. The German's proneness to errors is infuriating and despite a decent finish to the 2019/20 season, we can't go higher that 3/10.

Mustafi in action

Davinson Sanchez to Tottenham | £36.00m

Grade | 6/10

For a time, it looked as if the Colombian centre-back was going to be a mainstay in Spurs' XI. Game time has been hard to come by of late, though, but Sanchez is usually pretty dependable when he plays, so he more than merits his 6/10.

Eric Bailly to Man Utd | £34.20m

Grade | 4/10

It just hasn't worked out for Bailly at United. A combination of serious injury and persistent errors has seen his stock in the footballing world plummet in the past few years. But given he's just 26, the Ivorian still has time to turn his Premier League career around.

Luke Shaw to Man Utd | £33.75m

Grade | 5/10

Shaw has finally nailed down the left-back spot at United. However, given the other options at the club, that's not exactly the biggest achievement. The Red Devils' pursuit of Alex Telles this summer is evidence enough that Shaw still has a lot of work to do to be labelled a success at the club.

Shaw in action

A very mixed bag.

The average grade of the 15 players in question stands at 6/10, which isn't the greatest considering every single player cost way more than £30m.

Don't get your hopes up about Dias just yet, City fans.