3 players Jose Mourinho let slip away from Chelsea

In Atletico Madrid's commanding defensive performance against Barcelona on Wednesday there was one particular performer who shepherded away the repeated attacking threats with ease: Filipe Luis.

Jose Mourinho brought the left-back to Chelsea in 2014, but unceremoniously sent him back to the Spanish capital just a year later, despite a lack of opportunities in a blue shirt.

Luis is just one of many Mourinho let slip through the backdoor at Stamford Bridge, leaving those in the stands promptly ruing their departure as they showcase their considerable talents elsewhere.

Here are the three best players Chelsea should've kept, plus some notable mentions:

Kevin De Bruyne

Mourinho dubbed him a crybaby, a player not willing to apply himself in order to earn a first-team place. First at VfL Wolfsburg and now with Manchester City, De Bruyne has sensationally contradicted those claims, most recently showing a startling work ethic and unforeseen amount of leadership in a lighter shade of blue. Mourinho was very, very wrong.

The first half of Chelsea's 2015-16 campaign was dire, as the likes of Eden Hazard showed about as much creativity as a West Bromwich Albion back four and the hunger of a vegetarian at an abattoir. Mourinho paid for his team's failings with his job, but with De Bruyne's application and artistry, it could've been a very different story.

Romelu Lukaku

Diego Costa, Alexandre Pato, Radamel Falcao, and Loic Remy have collectively scored 14 Premier League goals. Lukaku has 18, and single-handedly decimated the Blues' backline when Everton turfed Chelsea out of the FA Cup in March:

Why Mourinho thought it wise to dump Lukaku is unknown - £28 million certainly isn't enough for a striker who was drawing fair comparisons to Chelsea hero Dider Drogba and who, at 22, has emerged as one of the Premier League's finest forwards, perhaps after City's Sergio Aguero and, some would argue, Tottenham Hotspur's Harry Kane.

Lukaku is linked with a return to Chelsea this summer, two years after making his move to Everton permanent, but should come at a huge premium.

Robert Huth

Though not the most graceful of centre-backs - certainly cutting a figure of years past rather than a defender of the modern mould - and with a surname which befits his ball distribution, Chelsea could've done with Huth's calming and physical presence this season.

Now, following a bargain fee reported to be in the region of £3 million, the German veteran has forged one of the most respective backline pairings with Wes Morgan, forming the foundation of a sensational title charge by Leicester City.

Although a succession of fine defenders have come and gone since Huth was sold to Middlesbrough in 2006, he could have provided some valuable backup in an injury-hit position this season. The aged duo of Gary Cahill and John Terry have looked particularly stiff-legged earlier this term under Mourinho, and even the untried Matt Miazga was handed opportunities under Guus Hiddink later in the campaign.

Notable mentions

Lassana Diarra: Sold to Arsenal, where he was again unfairly overlooked, before thriving at Portsmouth and picking up the 2008 FA Cup. He earned a transfer to Real Madrid where he won winners' medals in La Liga and the Copa del Rey.

Juan Mata: Two-time Chelsea Player of the Year under the management of Andre Villas-Boas, Roberto Di Matteo, and Rafa Benitez, but then surprisingly dropped to the bench upon Mourinho's 2013 appointment. Was sold to Manchester United in January 2014, and has since become a fan favourite.

Ryan Bertrand: Another young prospect who struggled to win a spot in the first team. He eventually moved on to Southampton on a permanent basis in 2015, becoming a regular left-back in Roy Hodgson's England squad.

Thorgan Hazard: Younger brother of Eden who, like compatriot De Bruyne, moved to the Bundesliga in search of regular minutes. Though not as gifted as his older brother, he has shown himself to be a competent dribbler at Borussia Monchengladbach and could've been a decent option off the bench.