It has been a fantastic 18 months or so for Liverpool.

The Reds won the Champions League last term, and they were within touching distance of winning the Premier League as well as they finished one point off Manchester City. In regards to the latter, specifically, that was made possible by the Anfield outfit's sturdy defence which conceded just 22 goals in 38 games. That was the least of any team in the competition.

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They have proven to be worth their weight in gold, and now it seems they are at the very top of their game. So much so, website Transfermarkt has now listed Trent Alexander-Arnold, Virgil van Dijk and Andrew Robertson as the three most-valuable defenders on the planet. They are said to be worth €110m (£99m), €100m (£90m) and €80m (£72m) respectively.

This has got the Liverpool fans talking on Twitter, and they have been quick to point out just how little the three cost in comparison to their combined reported current worth.

Indeed, the three certainly did not break the bank in the long run. Van Dijk did cost £75m in January of last year, which was a world-record at the time, but that has proven to be shrewd business, and Robertson cost just £8m in 2017. Alexander-Arnold, meanwhile, came through the club's academy and didn't cost a penny.

Despite them topping the list of defenders across the world, some people believe they have actually been undervalued - especially the Netherlands international.

Of course, these numbers aren't what they would necessarily fetch on the transfer market, but rather just a marker as to how much they are worth right now.

Some fans believe that one other man is missing from the list.

The 28-year-old is certainly a top defender, but injuries have stopped him from progressing at the rate he should have done. Considering he has played 41 times over the past 18 months - Liverpool have been on the field a fair few more times than that - his own £36m value does not seem too far off.

All in all, though, this is just another barometer of how good Jurgen Klopp's side is at the moment.

In other news, Liverpool are interested in signing this superstar.