Liverpool's season has brought much hope and optimism for Reds supporters with many now firmly of the belief the club can finally end their title drought that has lasted 26 years.

Jurgen Klopp has already ensured the squad was well prepared for the upcoming season. However, flaws currently exist in the present group, with many positions still needing upgrading for the Reds to ensure a title win come May.

Many Kopites may not agree with the statement, but Liverpool's frailties in defence could prove to be their Achilles heel in pursuit of a first Premier League title.

As previously witnessed with other title contenders, improvements must be made on a window-by-window basis with teams not resting on their laurels.

So, here are THREE players Liverpool should sell this January and THREE they should bring in as they aim to ensure the opening months of the campaign are not wasted.

IN - Jordan Amavi

Being honest, it's difficult to comprehend Jordan Amavi still being at Aston Villa following their relegation to the Championship if it weren't for his injury woes.

The French left-back was Villa's most impressive performer before a devastating knee problem forced him out of action for almost one year.

Now the time has passed and Amavi is starting to showcase his talent once again with the Villans. The former Nice left-back was a France U-21 international and widely tipped to replace the ageing Patrice Evra in the first-team, so he clearly has talent.

OUT - Alberto Moreno

What a disastrous signing Alberto Moreno has proven to be. The Spanish left-back was signed with high promise in July 2014 from Sevilla and was expected to solve Liverpool's long-term issue at left-back.

However, Moreno has instead proven worse than any previous full-back in recent times, and it's time the club cut their losses with him and try claim a portion of the £20million paid to Sevilla back.

IN - Virgil Van Dijk

Klopp would have to search far and wide to find a centre-back with better potential than Virgil van Dijk.

The Dutch defender continues to gain plaudits for his impressive performances for Southampton, and it looks likely he will continue to grow from strength-to-strength.

With a £25million release clause, Klopp would be foolish to dismiss Van Dijk considering Liverpool's horrendous issues defensively.

OUT - Mamadou Sakho

Not many people are aware of the off-field difficulties Klopp has faced with Sakho, but the French international's future at the club is seemingly over with his disciplinary issues during the club's pre-season tour, it would seem, the straw that broke the camel's back.

Klopp must attempt to find a potential suitor for Sakho for a reasonable price as he is yet to feature in the Premier League so far this season.

The German boss is struggling to ensure clean-sheets for his side, but Sakho obviously isn't seen as the answer to his problems.

IN - Quincy Promes

Promes is unquestionably the finest talent in Russian football at the moment.

The Dutch international has been sensational for Spartak Moscow over the past 18 months, and he continues to spearhead the Red and Whites' charge towards a league title.

Promes' ability could be described as similar to Sadio Mane's. However, the Dutch international may require time to adapt to the Premier League as the pace is somewhat different to that of Russian football.

OUT - Daniel Sturridge

It's not difficult to work out that Daniel Sturridge's relationship with Klopp is not overly healthy. The German manager refuses to allow Sturridge his chance to shine in the first-team when key players are missing through injury.

Now with the form of Divock Origi, Liverpool no longer need Sturridge as his injuries also continue to be an issue.

A struggling Premier League club would certainly love to take a gamble on someone with the credentials of Sturridge.