Liverpool vs Arsenal: Five things we learned as Jurgen Klopp's side edge Unai Emery's men on penalties after ten-goal thriller

Five things we learned: Mesut Ozil reminded Unai Emery of his quality and where can Jurgen Klopp find an alternative to Fabinho?

Shkodran Mustafi will struggle to turn around Arsenal's leaky defence

Unai Emery has made it crystal clear since the summer that Shkodran Mustafi is no longer in his plans for Arsenal’s Premier League outings.

But hope had built that the German could build some confidence up and extend his Arsenal career by playing a more minor role without the boo boys hounding him out upon his every move.

However, the defender’s mistake against Liverpool FC encapsulated his career in North London to date, sliding in unnecessarily to cost Arsenal dearly in the currency of goals conceded, their 19^th in their last six games at Anfield.

Alex Oxlade-Chamberlain’s low ball across the box was dangerous but a piece of play that did not make a goal inevitable, but the German went to ground in an attempt to clear the ball, and some ill fortune saw the ball cannon off his right foot onto his left leg and past Emiliano Martinez.

Mistakes from his teammates later down the line ensured that an Arsenal defence once again failed to see a game out when well positioned to do so, but they appear to never be too far away for the German, which render it very difficult to see him ever reclaim his starting spot at the Emirates.

Unai Emery’s Lucas Torreira gamble finally pays dividends

A notable change that Emery appears to have made tactically is the deployment of Lucas Torreira in a more advanced role.

It may seem a peculiar move given the club possess the likes of Mesut Ozil and Dani Ceballos in their roster, but often it has been the Uruguayan who has made those late runs into the box that Aaron Ramsey executed so well during his career at the Emirates.

And while at times this season Torreira has looked rather unsettled in the new role assigned to him by his manager, tonight’s goal, alongside the strike the midfielder netted at Anfield in the Premier League in August, highlighted the outcome Emery is attempting to achieve.

The offside flag should have been raised and VAR would almost certainly have ruled the effort out, but Torreira was in the right place at the right time to convert from close range after Ozil had set up Bukayo Saka.

Further examples will be required to get the Arsenal supporters on side, but tonight provided a glimpse of what runs from deep from Torreira could yield in goalscoring terms.

Experience and youth fall to the see-saw nature of cup competitions

With a combined age of just 34, Harvey Elliott and Gabriel Martinelli truly discovered the thrills and spills that English football can throw up.

Of course, Liverpool vs Arsenal is a fixture which has thrown up plenty in the past, most notably the 6-3 at Anfield in 2007, but on that occasion it was experience that largely shone through on that evening. Here it was youth - initially at least.

Elliott’s first ever Anfield outing began with a rather humbling experience which saw him concede possession to Ozil with a sloppy pass, and soon after the ball had beaten Caoimhin Kelleher due to Martinelli’s finish from Ainsley Maitland-Niles’ cross.

The strike was the Brazilian’s second of the game after he had smashed an effort into the roof of the net after some poor keeping from Kelleher, which saw two goals from one Carabao Cup game become four in two.

But as it so often does football has a way of clawing back at you when you least expect it, and it was Elliott who was the instigator of the blemish the Brazilian left on the game, stepping inside the Brazilian before the 18-year-old trod on his toes.

Yet experience can stumble at the same hurdle as youth, as James Milner proved by making no mistake from the spot, but then gifting Arsenal a fourth with a poor backpass which was complemented by a delightful flick from Ozil.

The Carabao Cup may be the least glamorous domestic reward, but it is still capable of producing golden and bizarre moments in equal measure.

Mesut Ozil delivered an excellent performance on his return to the Arsenal side (AFP via Getty Images) (Getty)

Mesut Ozil has staked a claim for a Premier League role

Amongst the hectic, fast-paced nature of the tie at Anfield, there was always one point of calm, as it was called this evening, for Arsenal.

Mesut Ozil’s languid style can at times be misinterpreted as a performance lacking in effort, but at Anfield it was exactly what a more youthful Arsenal side required.

He was instrumental of not only playing the delicate final ball as evidenced by Maitland-Niles’ goals, but also breaking up play to trigger attacks, which Martinelli benefited from.

Put simply, Ozil provided impetus, not just creativity, in the final third for the 65 minutes - something that has been lacking not only from Emery’s men in the Premier League, but also at times during the German’s career.

But here was a stark reminder that 31-year-old still has plenty to offer the Gunners - even if his substitution for Matteo Guendouzi was premature.

Jurgen Klopp still searching for Fabinho alternative

Alex Oxlade-Chamberlain’s first Anfield start against his former club was full of the potential that many had expected him to fulfil at the Emirates, with creativity in the first half supplanted by an eye-opening second-half screamer that may have topped his second goal in Genk.

It was a strike that in most games would have claimed the highly-coveted goal of the game award, especially in a thriller such as the tie this evening, but for Joe Willock’s arrowed effort.

But what goal fests also highlight are the deficiencies of both sides’ defensive units, and while Arsenal’s have been well-documented, Liverpool’s emerged from Fabinho’s absence and Adam Lallana's discomfort in a deeper role.

The hosts lacked an enforcer to stem the flow of attacks from Arsenal - allowing Ozil to roam freely and have a destructive impact on Liverpool’s Carabao Cup hopes, and Willock to run free before unleashing a fantastic effort past Kelleher

Liverpool may already have conceded at least three goals at home this month when Red Bull Salzburg were the visitors and nearly pulled off a miracle comeback, but the five goals they conceded at the back end of this month have confirmed that Klopp still has work to do to keep things tights in midfield when he chooses to rest the Brazilian.

Divock Origi rescued Liverpool on this occasion with two well-taken goals, and despite their recent history which suggests otherwise, Klopp faces a test to find a midfield combination which exhibits his side's best football while demonstrating a determined rearguard action.