Manchester City have spent £126million on full-backs already this summer - and we’re not even into the final month of the transfer window.

That’s more than the Premier League’s next biggest spenders Chelsea have splashed out on all their signings combined, represents 15% of the division’s total outlay and is just £27million shy of what Pep Guardiola spent during his first transfer window as Manchester City manager.

City are using their enormous financial muscle to address a long-standing oversight that hasn’t seen them invest in any first-team full-backs since an ageing Maicon was acquired for just £3million in summer 2012.

There was simply no way Guardiola could have gone into next season, attempting to further implement the Barcelona-esque philosophy that underpinned his mandate for the City job and justified an underwhelming first season in English football, still relying on Gael Clichy, Pablo Zabaleta and Bacary Sagna. Rather tellingly, all three were released earlier this summer.

Nonetheless, even amid a summer that could well see the Premier League encroach upon the £2billion spent mark, the figures still suggest City possessing more money than sense. After all, the Etihad outfit are now just £1millon shy of matching Real Madrid’s record of the most expensive transfer window from a single club dating back to summer 2009.

Whereas Los Blancos purchased a former Ballon d’Or winner in Kaka and a future four-time Ballon d’Or winner in Cristiano Ronaldo, however, the Citizens have invested the majority of their funds in Kyle Walker, who hasn’t even held down the No.2 berth in the England squad since his international debut in 2011, Danilo, who arrives in Manchester following two seasons as Dani Carvajal’s understudy at Real Madrid, and Benjamin Mendy, a 23-year-old who was hardly known outside of French football until Monaco’s impressive Champions League run last season.

Even bearing in mind how inflation in the transfer market has dramatically escalated since 2009, the immediate assumption is City have been taken to the cleaners. Some Tottenham fans believe the £50million for Walker represents better business on Daniel Levy’s part than Gareth Bale’s record-breaking move to Real Madrid - an argument further validated by Danilo arriving a week or so later for just over half the amount - and that deal reportedly convinced Monaco to bump up the price for Mendy, viewing him as a more talented player than the England international.

If those signings had been made in a different sequence at different times of the transfer window, the Citizens may well have saved themselves a small fortune.

Yet, City’s unprecedented spending on full-backs hasn’t taken place in a vacuum and if there’s one position where you do want to over-invest in the modern game, it’s arguably on the defensive flanks.

In fact, for all the jibes that have come their way over the deals for Walker and Mendy, Chelsea were prepared to pay around £10million more - a club-record £60million - to sign Juventus’ flying full-back Alex Sandro at the start of July, even after investing just shy of £20million in the same position through Marcos Alonso last summer - a fee that bemused many at the time.

Since then, Chelsea have spent that exact sum, £60million, on a new star striker in Alvaro Morata. You know the game has changed drastically when reigning Premier League champions are prepared to spend as much on a full-back as they are a centre-forward - and theoretically their main goalscorer for a title defence - when they already have a more than acceptable No.3 in place. Two including the versatile Cesar Azpilicueta.

For all the stunned responses to City’s spending too, the rising importance of full-backs has been a growing trend for some time, especially in the transfer market. In fact, full-back has gone from being the position the Premier League’s top six clubs spent the least on per player in summer 2013 to being the position the third-most has been spent on per player during the last two summers.

Equally, whereas fees for every type of player have steadily risen in the Premier League over the last four years, no position has experienced the same level of inflation as full-back - a staggering 546% from the average in summer 2013.

Even last summer, prior to City’s staggering full-back spending this year, the average amount spent per full-back since 2013 had risen by a division-highest 293%. Perhaps most tellingly, full-back is just one of three positions in which the average price per player hasn’t fallen behind what it was in 2013 over the last four summers, alongside attacking midfielders and strikers.

Suddenly, full-backs have moved from the fringes to the elite end of the transfer market, in the same bracket as those who operate in the middle-to-final third, where the cost of cutting-edge, match-winning quality continually soars.

These numbers are no mere coincidence; during that four-year period, the tactical utilisation of full-backs has revolutionised completely, climaxing with Antonio Conte winning the league last season by implementing a wing-back employing 3-4-3 system which was mimicked, either directly or using a variation of, by 16 Premier League sides on at least one occasion during 2016/17, including every club in the top seven.

That provided the biggest indication yet of how drastically the game has changed for full-backs, essentially becoming the new box-to-box engine rooms of any given team and accordingly moved from the defence to the midfield.

Rather intriguingly, central midfield - the position where dynamos once resided in almost exclusively - has experienced the least inflation over the last four years, during which time the average price per player has dropped twice.

Had it not been for summer 2014, the average amount spent on full-backs by top six clubs would have risen with every transfer window without fail. But the anomaly on this occasion was Luke Shaw’s move to Manchester United - a deal that, in hindsight, now appears ahead of its time for many reasons. Of course, the England international’s struggles at Old Trafford, both physically in terms of injuries and mentally in terms of questions over his attitude, suggest the then-Southampton teenager wasn’t ready for life at a major club.

But tactically too, Shaw had emerged as amongst the youngest of the new breed of dynamic, offensive full-back when he caught the Red Devils' eye, capable of providing width and penetration and marshalling entire flanks almost single-handed.

That resulting allowance to let the adjoining attacking midfielder line up considerably narrower caught the crest of a tactical wave in the Premier League, one Mauricio Pochettino has successfully taken to Tottenham to further increase its influence throughout the top flight, and spending a world-record sum for a full-back in Shaw three years ago very much felt like United were investing in the future.

That future is exactly what we see today; pretty much all Premier League clubs employing attacking full-backs on either side, so advanced many teams now use them as wing-backs, and it accordingly becoming one of the most expensive positions to recruit for, commanding the same kinds of transfer fees as attacking midfielders and centre-forwards.

Unfortunately for United, their attempt to stay ahead of the curve just hasn’t quite worked out, but the thinking behind the £30million spend on Shaw has been justified in the three years since his arrival by the tactical shifts throughout the wider Premier League.

Inevitably, City's full-back spending this summer has raised eyebrows that won't fall back into their resting position until Guardiola has indisputably reaped the rewards from it. But if the theory of full-backs becoming one of the most important positions on the pitch, something that particularly resonates with Guardiola's attacking philosophy, is correct or proves even truer in the coming seasons, then £126million will eventually be judged a fair price for staying at the tactical forefront of the modern game.

At this point, however, one thing is for certain. In the space of a single summer, City have gone from having comfortably the worst to arguably the best full-backs in the Premier League's top six. The coming season will show, rightly or wrongly, how important that actually is. My hunch, however, is that it will be the difference in the coming title race.

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