Last week, Chelsea finalised a £16million deal for Atletico Madrid defender Filipe Luis, a transfer that had been suspected and alleged by press in England and Spain for quite some time.

The Brazilian left-back has been brought in as a direct replacement for Ashley Cole, who switched his allegiances to Roma last week via a bosman move.

In terms of style, quality and proven credentials, the La Liga winner and Champions League finalist ticks all the boxes. But £16million, for a 28 year-old full-back who has never plied his trade in the Premier League before, is a heck of a lot of money - is this Chelsea's worst transfer thus far during Jose Mourinho's second spell?

I do not intend for that motion to be as pejorative as it initially sounds. Rather, since Jose Mourinho's return to Stamford Bridge in summer 2013,  the Blues have been exceptionally astute in the transfer market. The Luis deal, in terms of value-for-money, has a lot of competition.

Last January for example, Mourinho swapped a player he didn't want in Juan Mata for a player he desperately needed in Nemanja Matic and pocketed £16million in profit for the privilege. Likewise, this summer, he's already acquired La Liga's most potent goal threat in Diego Costa for a £32million fee - to think the same time last year Blues fans were complaining that their club hadn't dared to match Monaco's £54million bid for Ramadel Falcao or PSG's £53million spend on Edinson Cavani, despite the glaring inadequacies of the west London outfit's strikeforce.

Even some of Chelsea's more controversial deals from last summer have proved to be fruitful investments. An £18million swoop for Andre Schurrle raised eyebrows at the time, but over the course of the season his eight league goals in 30 appearances, in addition to his ability to play anywhere across the front three, has proved to be a vital contribution. Similarly, although Willian may not have paid back his £32million fee just yet - which is currently the club's fifth-most expensive signing of all time - few would debate that  the Brazil international is an excellent team player with all the attributes to succeed in the Premier League.

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Likewise, and to revert back from a brief digression, the whole footballing world appears to have gone left-back crazy this summer. Manchester United have already splashed out £30million on Luke Shaw, Sevilla have slapped a £20million price-tag on La Liga's version of Luke Shaw, Alberto Moreno, Tottenham are reportedly prepared to pay £12million for Swansea's Ben Davies - a 21 year-old who, although impressive in patches, is by no means a world-beater - and after ripping apart the Bundesliga last season and subsequently dazzling at the World Cup, Wolfsburg's Ricardo Rodriguez could be worth anything between £15million and £25million, depending on sources.

In comparison, £16million for a defender who played in last season's Champions League final, boasts four caps for Selecao and 376 competitive club appearances hardly seems a bad piece of business.

Furthermore, Filipe Luis is the epitome of the Mourinho mantra; at 6 foot he has the natural build of a centre-back, and whilst the rest of the continent has become obsessed with the new era of false full-backs, the 28 year-old is a throwback to more defensive traditions, having averaged 4.1 tackles per match last season - the third most of any player in La Liga. Most importantly of all, Luis has shone brightest under Diego Simeone, a man who shares Mourinho's organised anti-football philosophy and cult-of-personality management style.

But it almost feels as if last season didn't happen, of which I'm referring to the impeccable form of Cesar Azpilicueta. Usurping Ashley Cole from a spot he's held in the Chelsea first team for the best part of eight years tells its own story, all the more compelling for the fact that before Mourinho's arrival, the Spaniard was exclusively considered a right-back.

Indeed, the 23 year-old's transition from a roaming No.2 into arguably the Premier League's most defensively-assured No.3 has been nothing short of sensational, and for that reason alone I'd argue Filipe Luis is a player Chelsea don't actually need.

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Of course, the Blues still need a back-up option and it remains to be seen whether Mourinho will continue with Azpilicueta as his resident left-back, switch his loyalties to Luis or reach some kind of game-sharing arrangement between the two. The Brazilian was exceptional in the Champions League last season - Azpilicueta less so - and it's known Mourinho is eying the European trophy as his ultimate prize at Stamford Bridge.

There's also the option of returning Azpilicueta to his natural right-back position. To subscribe to that theory however, you'd have to ignore the fact Branislav Ivanovic made more Premier League appearances than any Chelsea player last season and, much like Luis, epitomises the aggressive and physical Mourinho philosophy.

But it would be a tremendous shame if Azpilicueta's development was stalled for the sake of an older player who in my opinion would only be a marginal improvement, if any at all. Alternatively, if Luis is to play second-fiddle to the Spain international next season, there's no question that Chelsea have overspent on a bit-part player.

Either way, in comparison to Chelsea's other shrewd transfer moves over the last twelve months, I find their capture of Luis incredible underwhelming.

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