Why Defence Is the Area Chelsea Need to Address in Final Week of Transfer Window

Pedro's Chelsea debut on Sunday told us plenty.

We had a glimpse of just how clinical the Premier League champions can be this season, with an added threat and dynamic to their attacking options.

It was also a moment that must have surely convinced Chelsea's money men that they need to dip their toes back in the market before the transfer window closes.

That time comes in one week and if Chelsea haven't strengthened their back line before then, there's every chance they will rue the decision not to.

Pedro's display against West Bromwich Albion doesn't mean Chelsea are going to successfully defend their title. It doesn't mean they're going to win the FA Cup, Capital One Cup or the Champions League, either.

There's still plenty more to do at Stamford Bridge to convince us Jose Mourinho's squad is capable of going the distance.

But it's a start and it needs to be followed up with at least one more signing to impact this team the way Pedro has.

We saw the holes in Chelsea's squad last season. They were light in key areas all over the pitch.

Beyond the first XI, Mourinho didn't have much to work with, which is why we saw some out-of-character displays at some key moments.

Top of that list was the away-goals defeat to Paris Saint-Germain in the Champions League. Despite winning the Premier League title, the manner of that defeat let a significant black mark on Chelsea's campaign.

Tactically there wasn't much between Laurent Blanc and Mourinho, but when it came to options over the 180 minutes, the PSG boss had much more to ask questions of Chelsea.

And as it turned out, Chelsea didn't have the answers.

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When things went wrong for Eden Hazard, there wasn't another player Chelsea could introduce to turn the tide.

When Marco Verratti used all his tenacity to dominate midfield alongside Thiago Motta, Chelsea looked lightweight. They were bullied in the middle and also lacked composure defensively.

Perhaps being the 2014/15 Premier League champions there was a thought at Chelsea that PSG was just one of those things, that playing against Europe's elite, any team can be overcome in such a way.

Yes, it happens.

Then came the loss to Manchester City this season and those same frailties reappeared. Chelsea were second best all over the pitch and it showed, only this time the defeat was even more alarming.

Mourinho's half-time substitution of John Terry showed how the external fears regarding Chelsea's lack of pace at the back has suddenly entered the manager's mind.

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The manager even said himself the the reason for swapping Terry for Kurt Zouma was to ensure his fastest defender wasn't on the bench.

Knowing the pace City have in attack, it was surprising Mourinho hadn't considered that in his selection for the game.

It does happen often, but Mourinho was questioning himself after what he had seen in that opening 45 minutes.

Signing Pedro has significantly helped the attacking dilemma, but with just Baba Rahman signed to bolster the defence following Filipe Luis' move back to Atletico Madrid, something needs to be done.

We've seen the pursuit of John Stones run and run, per Jamie Jackson at the Guardian, so now's the time to bring it to an end in a way that benefits Chelsea.

It's clear the Everton man has been Mourinho's long-term target so failure to get him will amount to a big problem. If Chelsea eventually go elsewhere, it will be close to accepting second best, regardless of who they sign.

There are other defenders on the market, sure, but when a club has pursued one man for so long, suddenly changing course and taking another option because of the looming transfer deadline, doesn't lend itself to sound planning.

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Chelsea have a plan for Stones and they need to make it work now otherwise the problems we've been seeing in these opening three games of 2015/16 are going to remain for some time yet.

Terry is far from past it at Chelsea, while Gary Cahill remains an exceptional defender and Zouma is a raw talent, capable of playing 20 games in 2015/16 as he continues to develop (not to mention his ability to play as an extra defensive midfielder).

An extra body is needed and not to simply make up the numbers. Chelsea need more options to adapt to games and cancel out opponents. They need other qualities that aren't yet available.

Arsene Wenger is often criticised for having one approach to winning games. When things blow up, the daggers are often drawn and his resistance to adapting is rightly questioned.

Without addressing their defensive problems in the here and now, Chelsea are tying their hands in much the same way.

And if they don't, it won't be long before the fingers start pointing.

Garry Hayes is Bleacher Report's lead Chelsea correspondent. All quotes were obtained firsthand unless otherwise noted. Follow him on Twitter @garryhayes