“I was in demand,” remembered Phil Babb. “I was on holiday and every other day I was reading the papers and I was going here, there and everywhere.”

Back in 1994, the player who was once rejected by his local club Millwall appeared to have the world at his feet. Fresh from his exploits for Republic of Ireland at the World Cup in the United States, Babb joined Liverpool on 1 September for £3.6m – a then British record fee for a defender. The very next day he was joined at Anfield by Wimbledon’s John Scales for £3.5m as Roy Evans set about attempting to transform the fortunes of a team who had conceded 55 goals in finishing eighth the previous season.

More than two decades have passed since then but, once more, Liverpool find themselves on the lookout for premium defensive reinforcements following a campaign that saw them concede more goals than any of the other top-four sides. But whereas more than a few eyebrows were raised in 1994 when Evans shelled out more than £7m for two centre-halves, the changing landscape of the modern transfer market means his successor was contemplating making Virgil van Dijk the most expensive defender in history until they were forced into a dramatic climbdown on Wednesday after being accused by Southampton of tapping him up.

Klopp must now find an alternative – and quickly – in an environment that saw Manchester City shell out £47.5m on John Stones last August and looks as if it will become more frenzied as the summer goes on.

“I don’t think they will ever be the same level as the strikers but the amount clubs are prepared to pay for outstanding defenders has certainly increased,” says Scales, who stayed at Anfield for only two seasons before moving to Tottenham. “The number of clubs at the top of the Premier League that had defensive problems last season shows there is a lack of depth in that area and that helps to drive up the price for those few that there are.

“There’s clearly a lack of top-class defenders who are available and clubs are prepared to pay ever more to get them, so that inflates the price. When you have Sunderland earning £100m for finishing bottom of the table then it shows just how much money teams have got to spend now. Add to that all the other teams from Europe’s top leagues and it quickly drives the prices up.”

David Luiz remains the costliest defender of all time after his £50m move from Chelsea to Paris Saint-Germain in 2014. That ranks only 14th in the overall list but after several higher bids were received by Napoli last summer for the Senegal defender Kalidou Koulibaly, it seems a matter of time before that is broken.

Will anyone meet the €65m (£56.4m) release clause for Athletic Bilbao’s defender Aymeric Laporte, here battling with Lionel Messi? Manchester City are thought to be weighing up an approach. Photograph: Ander Gillenea/AFP/Getty Images

“It’s a cliche but a player is worth what a club is prepared to pay for him,” says Scales, who works for the English Schools FA and as a pundit for Sky Sports’ coverage of the Eredivisie. “It’s very difficult to weigh up all the factors that must be considered but one of the most important things for a defender is maturity. There are exceptions to the rule but generally you want a defender who has three or four years more experience than a younger player.

“Attacking-wise you can take more of a risk to allow them to develop their talent in a slightly less pressurised way because you’re rotating them more until they have established themselves properly. A club will have more options offensively so some of them can be taken out of the firing line much more easily than expensive defenders that you’re buying to go in there and form a unit. You need that maturity and physical development to be able to do that because if you make a mistake it usually leads to a goal.”

Since the purchase of Eliaquim Mangala for an eye-watering £42m in August 2014, City have been particularly wasteful in their pursuit of a high-class defender to partner Vincent Kompany. Nicolás Otamendi arrived the following summer for £34m, meaning that the purchase of Stones took their outlay past the £120m mark and Pep Guardiola is thought to be weighing up a new approach for the France defender Aymeric Laporte from Athletic Bilbao, who has a €65m release clause. Meanwhile, Manchester United could surpass the £30m they paid for Eric Bailly last summer with the signing of Victor Lindelof from Benfica or to bring back their youth-team product Michael Keane from Burnley.

In terms of value for money, they may be better served taking a punt on one of the young Ajax defenders who performed so admirably in their run to the Europa League final. Matthijs de Ligt does not turn 18 until August but the Holland international has been tipped in his homeland to be the first £100m defender, and the Colombian Davinson Sánchez has been linked with Barcelona in recent weeks. According to Scales, however, things are never that simple.

“You’ve got to be wary of the Dutch League because the pace of the game isn’t as intense as the top leagues and players need time and space to adapt to moving up a level,” he says. “Having said that, if you’ve got the talent like both of them have then you have a great chance.

“The problem is you never know how they are going to do until they are thrown into the next level. Looking at the personality and mentality of the players is sometimes more important than their playing ability. That’s why it is so crucial that clubs do their due diligence properly.”

Most expensive defenders of all-time

1. David Luiz, £50m Chelsea to Paris Saint-Germain, 2014

2. John Stones, £47.5m Everton to Manchester City, 2016

3. Eliaquim Mangala, £42m Porto to Manchester City, 2014

4. Shkodran Mustafi, £35m Valencia to Arsenal, 2016

5. Nicolás Otamendi, £34m Valencia to Manchester City, 2015