It's a difficult question to answer, but who was the defining signing of Jurgen Klopp's time at Liverpool?

It's hard to look past the likes of Sadio Mane and Mohamed Salah, while plucking Virgil van Dijk from Southampton in January 2018 really did signify a change in tack, considering the £75m outlay.

And yet, was any signing really as vital as adding Alisson to the mix, the Brazilian goalkeeper arguably representing the final piece of the puzzle, following the prior woes of Loris Karius.

It was the kind of upgrade that the Reds needed to really kick on and become a properly dominant force again, both domestically and in Europe. Hopefully Andoni Iraola and co are set for something similar.

Why replacing Karius with Alisson was the final piece of the puzzle for Liverpool

Liverpool were a coming force under Klopp's watch, such a ferocious, thrilling team to watch in those early years, even while still lacking quality in key areas.

By the time of 2017/18, however, the Reds really did take things to a whole new level, with Salah spearheading the surge to the Champions League final.

Klopp's men were on the brink of greatness. And then came Karius.

At the start of the second-half, the German bizarrely put the ball on a plate for Karim Benzema to open the scoring, setting the tone for an evening that would end with another gaffe to allow Gareth Bale to make it 3-1.

Karius, to his credit, has since revived his career back in Germany with Schalke, but that was the day his Liverpool journey really ended, with FSG going big on Alisson that summer.

The rest, as they say, is history, with Klopp's men going on to win the competition a year later, their new 'keeper one of just three changes to the starting lineup from the 2018 showpiece.

Still the main man in the sticks in the present day, even with Giorgi Mamardashvili breathing down his neck, Alisson is now approaching 350 games for the club, having long been recognised as both one of the best in Europe and in the Premier League in his position.

It was an upgrade on Karius that the Reds needed to make, and they looked all the better for it, with the same perhaps true in the present day.

Why Liverpool have struck gold on their £60m upgrade

There's been plenty of negativity surrounding Liverpool's recruitment in recent years, and rightly so, with 2025 standing out as a particularly egregious summer of spending at Anfield.

The likes of Milos Kerkez and Jeremie Frimpong are yet to convince, despite the pair looking much improved on Tuesday night, while the marquee investment in Florian Wirtz and Alexander Isak has also backfired thus far.

And yet, while it is still early days, there have been signs of life from the 2026 cohort, with Victor Munoz notably netting that stunning equaliser against Nottingham Forest, while Jeremy Jacquet has been a class above at centre-back.

The young Frenchman was perhaps almost a forgotten man heading into this summer, considering the £60m deal was struck back in January, with injury having hampered the end to last season at Rennes.

Just a matter of weeks into life on Merseyside, however, and he's firmly a household name in his new surroundings, looking like the partner Van Dijk has long been waiting for.

Indeed, while he only made a 45-minute appearance against Tottenham Hotspur earlier this week, the 21-year-old showed his class again, memorably getting the better of Omar Marmoush with a fine piece of defending late on.

That combination of speed, strength and tactical awareness is why ESPN journalist Julien Laurens has tipped him to become "one of the best centre-backs in the world" before too long, with Liverpool already onto a winner it would appear.

Indeed, the man he has replaced at centre-back, Ibrahima Konate, was desperately poor for much of 2025/26, with the failure to agree a new contract with the experienced Frenchman no longer looking like such a concern due to Jacquet's form.

He was perhaps reaching Karius levels of haplessness, with club legend Jamie Carragher going strong back in April following the Champions League clash with Paris Saint-Germain, describing Konate as having looked "awful all season" as he "makes a mistake every game".

Like Karius eight years ago, in a key European contest, Konate was found wanting, the 27-year-old perhaps somewhat fortunate that Arne Slot had been left with almost no alternatives at centre-back across much of 2025/26, albeit while still regularly substituting the struggling late on in games.

The Premier League winner had played his part in Liverpool's success in recent years, but Jacquet already looks like a step up above, with TEAMtalk relaying how the club feel they have 'hit the jackpot' with this initially unsung signing.

Of course, the Reds' defensive woes haven't been solved entirely, but the club can rest easy again knowing they have a safe pair of hands alongside Van Dijk once more.

It's fair to say Konate was anything but that last term.