As the end of the 2018/19 campaign approaches, Liverpool are currently in a position to battle for the Premier League and the Champions League, arguably the two most prestigious titles in club football.

It's perhaps not being considered by many just yet, but it's plausible for the Reds to win both given their current state in each competition.

Jurgen Klopp's side are two points clear in their domestic league, albeit with one more match played, and have drawn FC Porto in the quarter-finals of Europe's elite tournament.

However, the reason that the club are somewhat on the verge of having their most rewarding season in decades is largely due to their impeccable recruitment in recent years.

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Since Klopp's arrival, the rise in prominence of Michael Edwards, and the incorporation of advanced analytics into proceedings, the decision-making at the club has been virtually flawless. This has led to relatively unearthed gems such as Mohamed Salah, Virgil van Dijk, Sadio Mane and Alisson Becker being signed before being snapped up by more established European heavyweights.

To continue their upward trajectory, the Reds will have to press on with their productive squad-building once more in the upcoming transfer window.

So with view to the summer, which areas need investment, and which players could fill the void?

What does the squad need?

Firstly, it's quite clear that a reliable centre back is required, with that reliability demonstrated both on the pitch and in terms of fitness. So far this season, van Dijk has played 3385 minutes in all competitions compared to Joe Gomez's 1452, Joel Matip's 1532, and Dejan Lovren's 996.

It remains to be seen whether one of the latter two will be sold, but it's quite clear that Klopp cannot rely on his current crop at present and thus, investment is required.

Andy Robertson has operated almost single-handedly as the club's left back for the entire season. The Scotland captain has played 3307 minutes, with his supposed backup option, Alberto Moreno, accumulating just 344 minutes. The regression of Alberto Moreno has been so notable that James Milner now appears ahead of him in the pecking order, hence the need for fresh competition, with the Spaniard leaving at the end of the campaign when his contract expires.

Another glaring void in the squad is the lack of a creative midfielder in the form of Philippe Coutinho or Nabil Fekir, who was previously chased. The likes of Jordan Henderson, Gini Wijnaldum, Fabinho and Milner all offer endeavour, but little in terms of a creative passing spark.

Alex Oxlade-Chamberlain provides a driving threat from midfield, but he's not particularly inventive with his passing and his traits are less valuable against highly defensive teams. It's arguable that Naby Keita holds the potential, but he's yet to showcase that convincingly in his first season in England.

Therefore, Klopp requires a player who's capable of playing in his midfield three, but also has the creative flair and the vision to unlock a defence.

Finally, Liverpool require a striker or a player that can operate across the front three similar to Mane, Salah and Roberto Firmino. Xherdan Shaqiri was brought in last summer, and although he's helped the cause, he doesn't appear able to play on the left or as a striker.

Divock Origi and Daniel Sturridge have filled in occasionally, but it's reasonable to suggest that Liverpool can now aim higher, with Sturridge also set to leave the club this summer.

These are four distinct areas whereby the squad is lacking in comparison to rival clubs.

It remains to be seen what the recruitment team will determine, but objectively, Liverpool require a centre back, a left back, a playmaking midfielder, and a versatile attacker. So, who could the club target?

Who could fill the void?

Centre back: Matthijs de Ligt (Ajax)

Sometimes, Liverpool are linked with a superstar name and supporters react with blind happiness at the prospect of him potentially playing on Merseyside. However, actual consideration into whether that player is suited to the club and the playing style is rarely deliberated, with the majority instead preferring to simply project how good the player is.

Jerome Boateng for example, was linked for around £40m last season despite the fact he was ageing, regressing, and would demand an excessively high wage; his transfer would have been unsustainable.

In the case of Matthijs de Ligt, it perhaps looks as though he's being suggested for similar reasons, because he's the next big thing and he has obvious superstar potential.

However, there genuinely appears to be no real downside to signing the young captain of Ajax, and all logic suggests that despite the likely high transfer fee, he would repay that investment and more comfortably.

The Dutch international is just 19 years old but is already captain of his club which indicates his personality, and he already plays alongside Van Dijk when representing his country, meaning a partnership has already been established.

Also, he's a very modern defender in terms of combining his composure on the ball with a complete defensive package. Also, in the crucial case of availability, de Ligt has accumulated 3588 minutes so far this season, which is even more than van Dijk.

A fee of £60m has been quoted for de Ligt's services, and although that seems excessive, the club would have an elite level defender for at least the next decade, with the worst-case scenario being that he's sold on before that to another club for an even higher sum.

Ajax's Matthijs de Ligt
Ajax's Matthijs de Ligt

Left back: Angelino (PSV)

In terms of left backs, the club will ideally want another Robertson, but the problem with that is finding a player with such a profile is quite rare.

Often, full backs that are so offensive-minded have little quality when engaging in duels, when required to soak pressure or when required to battle, with Moreno perhaps acting as the perfect example of that. Also, given the other key areas that require investment, it's unlikely that the club will want to dedicate a large portion of their budget on a full back.

It's reasonable to suggest that the recruitment team will track a player with a good base from which to work from, and Angelino offers that.

He's currently at PSV in Holland having interestingly left Manchester City last summer after a series of loan moves, but he's progressed significantly since, to the extent that Barcelona have shown some interest. He's Spanish, just 22 years old and he's contributed nine assists in 34 appearances which signifies his impact in advanced areas.

The pathway from the Dutch Eredivise to the Premier League isn't always smooth, with many struggling to acclimatise, but the risk of signing the Spaniard shouldn't be too costly, and his current profile offers encouragement.

Creative midfielder: Kerem Demirbay (Hoffenheim) or Julian Brandt (Bayer Leverkusen)

When delving into the underlying data of Europe's top leagues, it's quite remarkable that Kerem Demirbay is yet to be snapped up by a more established European club.

The 25-year-old's creativity is off the scale when considering his relatively deep role, but it's worth noting that a lot of that derives from his obligation to take virtually every set piece. These deliveries can result in his assists and Expected Assists (xA) rising, which isn't necessarily bad, but not all of his inventiveness is in open play.

Alongside Demirbay is Julian Brandt, a player that Liverpool have monitored in the past. This season, he's interestingly moved back to play largely on the left side of a midfield trio, but because of his attacking nature, he operates very offensively. Given that the club have a history with the player, as well as his new recent role in central midfield, it would make a lot of sense for him to be on the Reds' radar.

The midfield player profile radar comparing the two based on this season is pictured below.

Midfielder radar comparing output based on all competitions this season
Midfielder radar comparing output based on all competitions this season

It's notable that the two post similar shapes, which indicates that they assume almost identical roles for their respective teams, and their output is comparable.

The radar also stresses the previous point of how strange it is that Demirbay is yet to be snapped up. An advantage that Brandt has, though, is that he could be signed both as an attacker and as a playmaking midfielder, thus proving a creative midfield option as well as being a backup for Klopp's infamous front three.

Forward: Timo Werner (RB Leipzig)or Luka Jovic (Eintracht Frankfurt)

This recommendation is perhaps no surprise given the speculation, but there's a reason why Timo Werner has been consistently linked with Liverpool over a considerable period of time.

The German appears ideally suited to Klopp's front line, as he's fast, direct, versatile and has a superb underlying output based on this season. Werner is also just 23 years old, can play across the front three and crucially, he's right-footed, indicating that he could act as competition for Mane as the team's inside forward cutting in from the left.

The output of the German international is pictured in the attacker radar below in comparison to Mane and Salah this season in all competitions. Evidently, despite Salah in particular being renowned for his underlying performance, Werner is posting greater numbers in terms of scoring threat, considering aspects such as Expected Goals (xG), shots and goals per 90 minutes.

Player radar comparing offensive output based on all competitions this season
Player radar comparing offensive output based on all competitions this season

One more name worth mentioning is Luka Jovic, the Serbian who has made quite the introduction in the Bundesliga this season. He's on loan from Benfica to Eintracht Frankfurt at present, and there's a level of ambiguity surrounding his future.

If Klopp desires a strict no.9, though, in terms of a real penalty-box threat, Jovic is the man. The 21-year-old has scored 22 goals in 36 appearances whilst on loan, and his output is pictured in the radar below.

Attacker radar comparing offensive output based on all competitions this season
Attacker radar comparing offensive output based on all competitions this season

Overall, despite the required investment in these areas, it remains to be seen whether the club will actually sign a player for every one of the positions identified.

Klopp, Edwards and the recruitment team have often showed an innate ability of surprising - and will no doubt do so again this summer.