The ability to operate effectively in the transfer market is paramount for Premier League clubs.

Just look at Liverpool. The Reds have been brilliant in the transfer market in recent years.

They've signed players for cheap that have significantly bolstered their side, such as Andy Robertson.

And when they've spent big, such as on Virgil van Dijk, even those signings have looked like bargains.

But it wasn't just Liverpool that were making brilliant signings in the 2010s.

The Daily Mail have looked back at the past decade and have ranked the 20 best signings made by Premier League clubs.

20. Ayoze Perez | Tenerife to Newcastle | £1.5m

What a find this was. Perez was playing in the Spanish second division when Newcastle made the move for him.

He went on to play 195 times for the club, scoring 48 goals.

Newcastle made a substantial profit on Perez when they sold him to Leicester for £30m last summer.

19. Harry Maguire | Hull to Leicester | £17m

Maguire had just been relegated with Hull when Leicester decided to shell out £17m for him.

That proved to be a great decision as he became a key part of Leicester's backline.

His performances for his club side also helped establish him as a key figure for England.

Leicester sold Maguire for £80m last summer to Man United, making him the most expensive defender in football history.

18. Romelu Lukaku | Chelsea to Everton | £28m

Lukaku was never given a chance at Chelsea and, following a successful loan spell, Everton decided to make him their club-record signing in 2014.

In the next three seasons Lukaku would become one of the best forwards in the Premier League as he netted 53 times.

That earned him a £75m move to Man United in 2017, earning Everton a £47m profit. Not too shabby at all.

17. Wilfried Zaha | Man United to Crystal Palace | £6m

Zaha didn't cut it at Man United, meaning he made the £6m return to Crystal Palace in 2015.

Since then he's played 154 times for the club and scored 34 times.

He's been by far Palace's best player for the past five years and has recently been linked with a move to Chelsea.

Palace could make over a £70m profit for him if he does make the move. That wouldn't be bad business at all.

16. Philippe Coutinho | Inter Milan to Liverpool | £7m

Signed for £7m in 2013, Coutinho would soon become one of the best player's in the world.

The Brazilian midfielder scored 54 times in 201 games in his six seasons with the club.

He left on bad terms, though, as he forced through a £105m move to Barcelona in January 2018.

Still, Liverpool would have been happy with his service and they would have been even more happy with the £100m profit they made on him.

15. Dele Alli | MK Dons to Tottenham | £5m

Alli was coveted by many of England's top clubs in 2015 and it was eventually Spurs who won the race for his signature.

Paying £5m for a League One player five years ago was a fair bit of money but it looks like an absolute steal now.

Alli almost immediately established himself in the first team as he scored 10 goals in 46 games in his first season.

He's still at Spurs and thriving under Jose Mourinho.

14. Kevin De Bruyne | Wolfsburg to Man City | £55m

A lot of people laughed when Man City decided to pay £55m for De Bruyne, who struggled during his time at Chelsea.

But he's gone on to prove his doubters wrong. De Bruyne scored 16 times in his first season and has been brilliant ever since.

He's already notched 14 assists and seven goals this Premier League season alone.

De Bruyne is probably the best midfielder in the world right now.

13. Sadio Mane | RB Salzburg to Southampton | £11.8m

Little was known about Mane when he joined the Premier League in 2014.

But he would soon make his mark, scoring 25 goals across two seasons for the Saints.

His best moment in a Southampton shirt came when he broke the record for the fastest Premier League hat-trick, netting three times in two minutes and 56 seconds against Aston Villa.

He was sold to Liverpool in 2016 for £34m and he has since emerged into one of the best players in world football.

12. Mohamed Salah | Roma to Liverpool | £39m

Salah was Liverpool's top scorer last decade, having notched 84 times. What makes that tally remarkable is that fact he only joined in 2017.

Again, some people laughed when they heard Liverpool were signing a 'Chelsea reject' for £39m. They aren't laughing now.

What's he's done since arriving from Roma has been simply incredible.

11. Cesar Azpilicueta | Marseille to Chelsea | £7m

Azpilicueta has been extremely consistent since joining Chelsea.

He's made 363 appearances across eight seasons and is now club captain.

A £7m steal.

10. David de Gea | Atletico Madrid to United | £18.9m

De Gea was poor at the start of his United career. He looked too weak and many branded him a flop.

But Sir Alex Ferguson stood by him and he would go on to become the best goalkeeper in the world.

He's been suspect of late bit his performances in the middle of last decade means he's well worth a place on this list.

9. Yaya Toure | Barcelona to Man City | £24m

Toure was a wizard during his time at Man City.

He was extraordinary in the 2013/14 season, with his 20 goals leading City to the Premier League title.

The Ivorian scored 79 times in his 316 games for the club.

8. Eden Hazard | Lille to Chelsea | £32m

In 2012, Hazard famously revealed he would be joining Chelsea from Lille on Twitter.

Hazard was the club's most influential player for years, with the Belgian helping his side to two Premier League titles.

But all good things had to come to an end as he signed for Real Madrid in a deal worth €150 million last summer. He left Chelsea as a club legend.

7. Luis Suarez | Ajax to Liverpool | £22.8m

Perhaps the most controversial Premier League players of all-time, Suarez's performances on the pitch made up for his poor behaviour.

He scored 82 times for the club in his four seasons.

Liverpool made a £43m profit on him when he left for Barcelona in 2014.

6. Robin van Persie | Arsenal to Man United | £22.5m

Man United shocked the Premier League when they announced the signing of Van Persie from rivals Arsenal in 2012.

He was one of the best strikers in England's top tier at the time and he continued to prove that during his three-season spell with United.

The Dutchman was unplayable in the 2012/13 Premier League season. His 26 goals carried United to the title that campaign.

5. Andy Robertson | Hull to Liverpool | £8m

A few eyebrows were raised when Liverpool signed Robertson in 2017. Why would Liverpool spend £8m on a player who had just been relegated with Hull?

The Scotsman struggled to start his career at the club but he never looked back when he got his chance.

Fast forward two-and-a-half years and Robertson is now considered by many to be the best left-back in the world.

4. Virgil van Dijk | Southampton to Liverpool | £75m

Many football fans couldn't comprehend Liverpool breaking the world-record fee for a defender to sign Van Dijk in 2017.

But the Reds knew what they were doing and he's turned out to be a £75m bargain.

The Dutchman has almost single-handedly transformed Liverpool's defence from a liability into a strength.

He's now the best defender in the world and narrowly missed out on the 2019 Ballon d'Or.

3. David Silva | Valencia to Man City | £24m

Silva is arguably Man City's best player ever.

He's been a key part in a City team that won four Premier League titles last decade.

The Citizens will struggle to replace him when he leaves in the summer.

2. N'Golo Kante | Caen to Leicester | £5.6m

Very few English fans knew Kante when he signed for Leicester in 2015. But he soon announced himself to the world.

His energy in midfield was crucial as Leicester produced the biggest footballing shock in recent times by winning the Premier League title in the 2015/16 season.

Riyad Mahrez would win the PFA Player of the Year award that campaign, but Kante was arguably even more influential than his teammate.

Unfortunately for Leicester, they couldn't keep hold of Kante as he moved to Chelsea for £32m after just one season.

But he will always be appreciated by fans of the East Midlands club for what he did during that remarkable season.

1. Sergio Aguero | Atletico Madrid to Man City | £38m

Aguero's consistency in front of goal for Man City since signing in 2011 has been insane.

He's scored more than 25 goals in seven of his eight full seasons and he's set to hit that mark again this campaign.

In total, he's netted 245 times 357 appearances for the Manchester side. Extraordinary numbers.

The fact that Liverpool have five signings on the list is just testament to how good their transfer business has been in the past few years.

Man City, too, have nailed it in the transfer market.

The Citizens have had a bottomless pit of money over the past decade, which hasn't always been spent wisely, but they hit the jackpot with De Bruyne, Toure, Silva and Aguero.

With the latter, he's well worth being named the Premier League signing of last decade.

The Argentinian has been remarkable over the past 10 years and is arguably the best striker in Premier League history.

Spending £38m on him in 2011 was a lot of money at the time. But he was worth every single penny.