A quick glance at the most expensive transfers in Liverpool's history paints a telling picture.
There are the the likes of Virgil van Dijk, Alisson Becker and Luis Diaz, the big-money signings who have proven the worth of such an expensive outlay. Mohamed Salah and Sadio Mane are examples of players who, even at transfer fees in the tens of millions, have been a bargain.
Present too are the failures, neither Andy Carroll nor Christian Benteke able to justify their cost. Plus there are the new boys, with Darwin Nunez poised to lead the way should the Reds have to pay out fully on their £85million investment. January arrival Cody Gakpo is the newest name on the exclusive list.
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But there, standing as the fourth-most costly Liverpool player of all time, is Naby Keita. And almost six years since his arrival was first confirmed, the Guinean remains the Reds' most divisive squad member.
It's worth remembering that when Liverpool agreed in August 2017 to trigger his £48m release clause plus a £4.75m premium, it made Keita the club's most expensive signing, although by the time he made a competitive appearance he had been surpassed by both Van Dijk and Alisson.
The almost 12-month wait for Keita to switch from RB Leipzig ultimately proved a millstone around the midfielder's neck, allowing expectation to build to an almost unhealthy level. Rarely has a player had a full year being scrutinised by supporters in the knowledge he would soon be a Liverpool player.
Indeed, it's worth noting the Reds have since not made public any pre-arranged deals until the time approached for the player to make the move.
Now, as he celebrates his 28th birthday today, Keita appears to be coming to the end of his Liverpool career, talk over a new contract offer having gone silent for several months and, with the player now able to open discussions with clubs from abroad, interest arriving from several potential suitors. The Reds are poised to lose the midfielder for nothing come the end of the campaign.
Only the most mean-spirited could call Keita's time at Anfield a failure. He was important in helping seal Liverpool's first-ever Club World Cup triumph, started both the League Cup and FA Cup final wins over Chelsea last season and easily made enough outings to earn a Premier League winners' medal in 2020.
But even the Guinean's most ardent supporters would be hard-pressed to convince anyone he has been an outstanding success.
Keita, of course, has seen his time hampered by continued injuries, which have restricted him to just 127 appearances and 11 goals over four-and-a-half campaigns. Last season was his most productive in terms of outings, making 40 in total.
Despite his plethora of fitness issues, mentally Keita has proven himself rather more durable. Many of his injury issues have come at unfortunate times - such as during the first half of the Champions League semi-final at Barcelona, or the day before the UEFA Super Cup final against Chelsea - while few wouldn't have been surprised had Keita not played again after being given the hook before half-time in the Champions League quarter-final at Real Madrid two years ago. Yet on each occasion, he has dusted himself off and gone again.
Intriguingly, Keita has started three of the four major Liverpool finals for which he has been available, along with three of four semi-final matches. If he's fit, Klopp has regularly turned to him on the big occasion. That, though, is the big 'if' that will perhaps be the player's legacy.
Having missed the first part of this season, Keita has started the last four matches as Liverpool look to revitalise their midfield and campaign. Klopp, as ever, has seen no issue picking a player approaching the end of their deal provided he remains useful.
But regardless of opinion on the midfielder, there is one matter on which everyone is in agreement. Keita remains the ultimate Anfield enigma.
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