Liverpool have had a simply sensational summer so far but there is one glaringly obvious mistake they are making.

The Reds are taking the challenge of retaining their title very seriously, with the club being ruthless when it comes to both incomings and outgoings.

They have only recruited the best, and after spending close to £300m, they are still not done yet and want a few more additions before the new season rolls around.

Outgoings are also expected to make room, suggesting that Liverpool are being very efficient and smart, although that might not be the case.

There is one thing that they could be getting very wrong and, although on the surface it might not look like too much of an issue this summer, there is a very strong chance that it might be and completely derail their title defence.

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Liverpool should be prioritising a centre-back

It really has been something of a ‘Galactico’ transfer window for the Reds, and it could be about to get even better if they do end up getting Alexander Isak.

However, it is all well and good signing world-class talent and having the best attack in the league, but a defence is still needed, and Liverpool could be in trouble where that is concerned.

Pre-season has shown that the Reds are susceptible to counter-attacks, and although there is still time to sort this, injuries to anyone in defence could cause a big problem.

Liverpool currently have three first-team centre-backs, although one is 34 and the other two are very injury-prone.

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So, going all-out for another striker when they have just signed one for up to £79m seems a little reckless given the frailties at the back, suggesting they really should turn their attention to that instead.

The Reds are said to want a young defender that can take over from Virgil van Dijk eventually, but based on their lack of options, at least another one is needed on top of that, preferably an experienced one too.

That being said, another £200m is what Liverpool will likely need to spend this summer, taking their total spending to around £500m.

So, a big decision needs to be made. Do they prioritise Isak or be sensible and reinforce the defence that is in desperate need of a revamp?

Liverpool should sign Marc Guehi and Joel Ordonez

The clear frontrunner as Liverpool’s new centre-back is Marc Guehi, a player the Reds really should make a move for as Crystal Palace are keen to sell to avoid losing him on a free next summer.

The Englishman could cost around £45m, but the experience and quality he would bring would make it worth it, especially as they risk losing out on him next year as interest in him will only increase tenfold.

Then, a younger defender that fits the ‘usual age profile’ of between 18-22 is needed, and Club Brugge’s Joel Ordonez might be the best option.

The Ecuadorian is 21, has Champions League experience and has time to develop, making him an excellent fourth or fifth choice.

Liverpool fans will want Isak desperately, which is fine, but at least one centre-back simply has to arrive or they could be in big trouble.