The money Liverpool could miss out on if Coutinho joins Reds from Barca

Liverpool sold the Brazil international for £142m in January 2018, but the Reds are yet to have the fee in full

It's increasingly looking like one of the best transfer deals in Liverpool's 127-year history.

The Reds' sale of Philippe Coutinho to Barcelona in January 2018 was one that few - if any - wanted to see come to fruition from a Liverpool perspective at time.

Least of all Jurgen Klopp, who was hoping to keep the Brazil international for the long term after watching him light up Anfield with a string of brilliant displays in the first half of the 2017/18.

However, Coutinho's head was turned and his heart was set - Liverpool could do little but negotiate the best possible deal for them.

Michael Edwards, to the eternal credit of Liverpool's sporting director, did so with an aplomb he has made his trademark.

Liverpool struck a deal worth a total of £142million with Barcelona, making the fee the biggest ever the Reds have earned from selling a player.

It was also the biggest transfer a British club have been involved in, comfortably trumping Manchester United's £89m move for Paul Pogba in 2016.

The transfer was worth an initial £106m with a further £36m in add-ons centred around a number of clauses related to trophies won and milestones passed.

Back-to-back La Liga titles for Coutinho at Camp Nou may have seen the Reds earn closer to the full sum, but no such figures have been made public, while Barca haven't won a Champions League since they signed the Brazil international.

In May, Liverpool pocketed a further £4.3m last season after Barca made it to the quarter-final stage of the Champions League.

They were, of course, eliminated in the semi-finals by Liverpool, ensuring the £4.3m clause was triggered, bringing the overall total up to a minimum of £110.3m.

One clause that is believed to be in the contract is a £17m fee that will be paid in full when the attacking midfielder represents the La Liga champions 100 times.

His last appearance for Barca - the 2-1 defeat to Valencia in the Copa del Rey final - was his 75th for the club since he joined in January 2018.

It has been reported that the Reds earn £4.4m for every 25-game milestone Coutinho reaches, meaning they have banked £13.2m so far.

Liverpool would be confident of earning the full £17m sum if the Selecao star stays at Camp Nou this summer, but given the intense daily speculation, that is far from certain at present.

Twenty-five more appearances for Coutinho at Barca takes Liverpool's total up to £127.3m, but that total figure hangs in the balance until the close of the European transfer window on September 2.

As a result, Liverpool have so far earned £123.5m for the 27-year-old, leaving them £18.5m short of the fee that made Coutinho the third most expensive transfer in history 18 months ago.

The fee is an incredible amount of money for a player who cost the club less than 10 per cent of that when they brought him to Anfield for £8.5m in January 2013.

Edwards' transfer work was lauded even further after it was revealed that he struck a deal that effectively prohibited Barcelona from re-entering the market for any more Liverpool players until the summer of 2020.

In November last year, the ECHO reported that Edwards insisted that a €100m (£89m) premium be placed on any Reds player the Catalans wanted.

Those terms meant Barcelona were hugely unlikely to return to the table for the likes of Mohamed Salah, Virgil van Dijk or Roberto Firmino.