Over the last few summers, Chelsea’s missed opportunities in failing to bring the most exciting members of their controversial loan army through to the first team has been a recurring subject of discussion.

During this transfer window alone, we’ve seen Romelu Lukaku earn a £75million move to Manchester United by scoring 68 goals in four seasons at Everton, Nathan Ake complete a £20million move to Bournemouth after a successful loan spell at the Vitality Stadium last season and Mohamed Salah return to the Premier League with Liverpool after a potent stint in Serie A.

But with today making exactly one year since the Blues finally offloaded Marko Marin, a £6.5million acquisition whose Chelsea career consisted of just six Premier League appearances and four loan spells before being sold to Olympiacos for just £2.5million, it’s worth remembering that not every addition to Chelsea’s loan clan has been quite so successful in footballing and financial terms.

So here’s a look at the opposite end of the spectrum; the members of the loan army who, like Marin, either have or probably will cause Chelsea more grief than joy.

Marco van Ginkel

Signed from feeder club Vitesse for £8million, Marco van Ginkel was tipped for big things until suffering an ACL injury just four games into his Chelsea career.

The Dutchman’s never quite recovered from the seven-month layoff and is yet to make another appearance for his parent club, instead spending the last three seasons out on loan at AC Milan, Stoke City and PSV.

He re-joined the latter club temporarily once again this summer, but not before Chelsea rather bizarrely decided to extend his contract. It seems someone at Stamford Bridge still thinks the club can get a return on their original investment, but that appears unlikely.

Patrick Bamford

In fairness, Chelsea did manage to turn a £4million profit on Patrick Bamford, despite never using him in a competitive fixture throughout his five years on the books at Stamford Bridge.

But considering the high hopes placed on him as a youngster, the now-Middlesbrough forward has unquestionably failed to live up to his billing – when signing him from Nottingham Forest as a teenager, the club would have hoped to one day rake in double figures for the English striker.

From 26 Premier League outings for four different teams to date, Bamford has just netted one goal. He’s also yet to score for Boro in the Championship this season.

Matej Delac

Technically Chelsea’s longest serving player, Matej Delac hasn’t got anywhere near the Chelsea first team since arriving in 2010, let alone make a competitive appearance.

Instead, the Croatian goalkeeper has undergone a staggering nine loan spells, making 114 outings in total for clubs as exotic as Sarajevo, Excel Mouscron and Vitoria de Guimaraes.

Alleged to have paid £2.7million for the 6 foot 3 shot-stopper’s services, Delac looks almost certain to leave the club on a free transfer at some point in the coming years.

Baba Rahman

A somewhat accidental and incredibly costly member of Chelsea’s loan army, Baba Rahman was brought in at a cost of £14million rising to £22million to serve as understudy to Cesar Azpilicueta at left-back.

But after just a handful of appearances it became clear the Ghana international wasn’t up to the challenge and at the end of his first season in west London, he was loaned back to the Bundesliga where he’d gained a prodigious reputation with Augsburg.

Last term was spent at FC Schalke and although the defender didn’t disappoint to the same degree, Chelsea are unlikely to get their money back.

Wallace

Once billed as Brazil’s next great flamboyant full-back, Chelsea forked out £4.86million to land Wallace in 2013 after an incredibly bright start to his career with Fluminense.

Work permit complications forced the South American into the loan army route regardless of any plans Chelsea managers had for him and safe to say, it hasn’t worked out too well.

Now 23, Wallace appears further away from the Blues first team than ever before, spending last season out on loan at Gremio back in his native Brazil. Three loan spells in Europe saw him make just 27 league appearances.

Kenneth Omeruo

A similar story to Wallace, much was expected of Kenneth Omeruo after arriving at Chelsea – especially as he began to make himself a near-permanent fixture in Nigeria’s starting XI.

But the young defender’s struggled to realise his full potential and at the age of 23 is still waiting for the chance to test himself in a major European top flight, having spent his career on loan in the Eredivisie, the Championship and the Turkish Super Lig.

Michael Hector

A signing that made little sense at the time and even less now. Chelsea snapped up Michael Hector on Deadline Day 2015 and immediately loaned him back to Reading, where he endured another solid but largely unspectacular campaign.

This season, the 25-year-old is back in the Championship once again with Middlesbrough following a season in the Bundesliga with Eintracht Frankfurt.

The Blues may one day make a profit on their original £5.4million spend, but it surely won’t be by much.