They are three of the star performers in the Premier League so far this season, scoring and creating goals for fun as their teams challenge towards the top of the table.

But there is a common thread that links Manchester City maestro Kevin De Bruyne, Manchester United striker Romelu Lukaku and Liverpool magician Mohamed Salah.

They all played for Chelsea, only to fail to make an impression at Stamford Bridge and move on to launch their careers elsewhere.

So should Chelsea now regret letting them go? We take a look at what happened back then, what has happened since and what is happening now.

Kevin De Bruyne is enjoying an exceptional season as Manchester City top the Premier League

KEVIN DE BRUYNE

Chelsea 2012-2014; sold to Wolfsburg for £18million in January 2014; now at Manchester City

By common consensus the best player in the Premier League right now as Manchester City storm clear at the top, it is sometimes easy to forget that De Bruyne was once a Chelsea player.

A playmaker prodigy with Genk in his Belgian homeland, De Bruyne was signed by Chelsea on the January deadline day in 2012 for £7m, signing a five-and-a-half-year contract that was undoubtedly a vote of confidence in a 21-year-old.

Of course, De Bruyne wasn't the stylish, polished player we see now and then-manager Roberto Di Matteo, conscious of squad size and limited opportunities, loaned him to German side Werder Bremen for the 2012-13 season.

De Bruyne in action during one of his few Premier League outings for Chelsea, in August 2013

In action for Chelsea during a pre-season match against the Seattle Sounders in 2012

De Bruyne knuckled down in the Bundesliga and enjoyed a successful loan spell, scoring 10 times and contributing 10 assists for Werder giving a glimpse of his talents.

Plenty happened at Stamford Bridge in the meantime - Di Matteo left, Rafa Benitez came and went, and Jose Mourinho returned in the summer of 2013 for his second spell.

A number of German clubs were sniffing around De Bruyne, but it was Mourinho that personally intervened and assured the Belgian that he had a part in his plans for the season ahead.

That didn't materialise. Though De Bruyne did get his first experience of the Premier League and the Champions League, he never got a run in the side and it became increasingly apparent by the winter he was surplus to requirements.

In January 2014, Chelsea sold a frustrated De Bruyne to Wolfsburg for £18m, making a healthy profit for a player who'd only played nine competitive matches for them.

The Belgian made just nine appearances for Chelsea before being sold to Wolfsburg

A rare bright moment for De Bruyne as he scores for Chelsea in the 2013 International Champions Cup against Milan in New Jersey

Once again, the Bundesliga proved to his liking and De Bruyne performed consistently with high class and quality for one-and-a-half seasons. In 73 matches, he scored 20 goals and assisted with 37.

Named Germany's Footballer of the Year in 2015, it wasn't long before De Bruyne was attracting attention from leading clubs once again and when City came in with a £55m bid in August 2015, Wolfsburg were powerless to resist.

Although unproven in the Premier League, City clearly believed De Bruyne had the world class potential to justify a club record fee that was the second most expensive signing by a British club at the time.

They have been proven spectacularly correct. De Bruyne has become the best creative craftsman in the Premier League, with 46 assists in 106 matches for City, not to mention 26 goals.

His form this season has taken him to another level, with plenty of pundits speculating that he could soon be the best player in the world.

His second-half winner in City's 1-0 success at Stamford Bridge back in September will have been particularly sweet for the Belgian.

Should Chelsea regret selling De Bruyne?

Yes. At the moment, he is the best player in the Premier League and arguably in the top five in the world, while continuing to get better all the time.

It's difficult to know whether De Bruyne would have developed in the same way at Chelsea because at Wolfsburg he was clearly the star turn. Competition for places is always fierce at Chelsea.

But the overriding feeling at the moment is that Chelsea made a mistake in not keeping him and he fell into the clutches of a rival, with astonishing results.

De Bruyne takes particular pleasure in scoring City's winner at Chelsea back in September

De Bruyne's City have left Chelsea and all their other rivals lagging behind this season

ROMELU LUKAKU

Chelsea 2011-2014; sold to Everton for £28m in July 2014; now at Manchester United

Another brilliant Belgian signed by Chelsea at a young age after making a splash in his teenage years, only to find the pathway to stardom at Stamford Bridge blocked.

Lukaku burst onto the scene as a teenager at Anderlecht, scoring 19 goals in the 2009-10 season and 20 the following year.

Such feats in front of goal don't go unnoticed for long, particularly when you're a teenager, and Chelsea beat competition from rivals to sign him on a five-year contract for an initial £10m in August 2011.

Time was on Chelsea's side with Lukaku and, although Andre Villas-Boas gave him a taster of the first team, Chelsea's intention was always to get him experience out on loan.

Romelu Lukaku's time at Stamford Bridge was mainly a tale of frustration and loan spells

There were high hopes for the Belgian when he was signed from Anderlecht in 2011

This clearly came as a disappointment for the young striker, who wanted to make his mark in England. He didn't touch the Champions League trophy after Chelsea's 2012 win after failing to play a single minute of the campaign.

In true Chelsea style, Lukaku was packed off on loan, initially to West Bromwich Albion where he found the Premier League much to his liking and scored 17 times in 35 games while always maintaining his intention to make it at his parent club.

'My aim is to play at the Bridge and to be a legend over there in the future,' he said in February 2013.

Despite outscoring all of his Chelsea team-mates during his loan spell at The Hawthorns, it quickly became clear that Lukaku didn't feature in new manager Mourinho's plans and he went off to Everton for the season.

This was on the final day of the transfer window, so must have come as a disappointment. Nonetheless, Lukaku again performed very well, scoring 16 times to help Everton to a fifth-place finish with a club record 72 points.

Lukaku in one of his 15 first-team appearances for Chelsea, against Fulham in 2011

The Belgian celebrates scoring against Real Madrid in an International Champions Cup match

Lukaku had done everything asked and clearly demonstrated that he could score regularly in the Premier League, but the signing of Diego Costa from Atletico Madrid in the summer of 2014 suggested he wouldn't get his chance at Chelsea.

Sensibly, Lukaku signed permanently for Everton, netting Chelsea a handsome £28m in the process and picked up where he left off.

Goal returns of 20, 25 and 26 in all competitions during his three seasons with Everton after that underlined his status as a world-class striker and the elite clubs renewed their interest.

He was linked persistently with a return to Chelsea, who were willing to break the bank to get him back. In fact, manager Antonio Conte identified him as a key summer transfer target.

But the Blues were beaten to the chase by Manchester United, who persuaded Lukaku to remain in the North West in a deal worth an initial £75m with a potential £15m extra in add-ons.

And Lukaku made a blistering start to life at Old Trafford, scoring 10 goals in his first nine appearances to beat the club record established by Sir Bobby Charlton.

However, October proved a barren month for the striker, who hasn't scored now for United since September 30.

The big Belgian striker doesn't hold back after scoring against Chelsea for Everton in 2016

Should Chelsea regret selling Lukaku?

The fact Chelsea were so keen on re-signing Lukaku over the summer does suggest there are some regrets at how the Belgian went on to establish himself as one of the Premier League's best strikers.

And while there would have been some annoyance at being beaten to his signature by United, the fact Alvaro Morata made such a brilliant start to life in England has eased concerns.

In the time Lukaku was at Everton, Chelsea won the Premier League twice, so it isn't as though they struggled for firepower.

Chelsea have managed to get a top quality striker in Morata and any regrets about Lukaku are likely to be left far behind now.

Romelu Lukaku in action for Manchester United at Chelsea last Sunday. Chelsea won 1-0

MOHAMED SALAH

Chelsea 2014-2016; sold to Roma for £13.5m in August 2016; now at Liverpool

Mohamed Salah's stunning form for Liverpool this season, which has seen him score 12 goals in all competitions, will have come as a shock for those who remember the Egyptian labouring during his time at Chelsea.

He arrived in London from Basle in January 2014, commanding a fee in the region of £11m on the strength mainly of his Champions League and Europa League performances for the Swiss club.

Chelsea weren't short of wingers, with Eden Hazard, Andre Shurrle, Oscar and Willian in the squad, but Mourinho actually played Salah quite a lot in the Premier League during the second half of that season.

Salah would no doubt have been encouraged but, by the start of the following season, the picture had changed and he played a mere 30 minutes of league football before January.

Egyptian winger Mohamed Salah also suffered a frustrating spell when at Stamford Bridge

Salah did initially feature quite a bit following his arrival at Chelsea - midway through 2013-14

The sight of him being brought into the starting line-up for an FA Cup fourth-round tie against Bradford City - lost 4-2 after leading 2-0 - was a sorry one and a loan to Fiorentina on deadline day didn't come as a surprise.

What was surprising was the length of the loan - 18 months - and that signalled that Salah, even at the age of 22, had been dumped on the very large Chelsea scrapheap.

Salah produced some good form at Fiorentina but was reluctant to return for a second season and joined Roma instead. Again, Serie A was to his taste and an excellent 2015-16 season saw him score 15 goals and supply nine assists.

By now, there was never any question of Salah, very much the forgotten man, returning to Stamford Bridge and Antonio Conte sanctioned his sale to Roma for £13.5m, meaning a small profit on someone who'd only made 19 appearances.

But the minutes quickly dried up for Salah at the beginning of the 2014-15 campaign

He was left to play a bit-part role in matches such as this League Cup visit to Shrewsbury

Premier League scorers 8 - Sergio Aguero (Manchester City); Harry Kane (Tottenham) 7 - Alvaro Morata (Chelsea); Romelu Lukaku (Manchester United); Raheem Sterling, Gabriel Jesus (Manchester City); Mohamed Salah (Liverpool) Advertisement

Last season saw Salah excel at the Stadio Olimpico once again, with 19 goals and 15 assists, and it proved his return ticket to the Premier League.

Jurgen Klopp, suitably impressed by the lighting-quick winger's numbers, evidently saw that he would click into his style of play very easily and they paid £38m to bring him to Anfield.

So far, that is looking like money well spent, with Salah doing everything for Liverpool that he didn't do at Chelsea.

A dozen goals in all competitions have been scored, including seven in the Premier League which puts him on a par with the far more expensive strikers Lukaku and Morata.

Just as Klopp had hoped, Salah has fitted into Liverpool's turbo-paced, counter-attacking game seamlessly.

Should Chelsea regret selling Salah?

It's highly unlikely they will, regardless of how well he performs at Liverpool. It was a strange signing at the time, given Chelsea's abundance of attacking talent, and nobody was surprised when Salah didn't get much game time.

He is undoubtedly a better player now, but Chelsea, with the likes of Hazard, have excelled in the meantime.

They remain above Liverpool in the table and are likely to remain there until the end of the season.