For the first time since his departure from the club in January 2018, Philippe Coutinho is about to share the same pitch as Liverpool in a Premier League match. His Aston Villa side are scheduled to host the Reds on Tuesday night in what could be a truly decisive bout.
His departure from Anfield was dramatic at the time. Jurgen Klopp was steadily improving the landscape on Merseyside, yet the Brazilian seemed intent on joining Barcelona.
Since, Liverpool have progressed from strength to strength. The Reds have delivered Champions League and Premier League titles under their German coach, while also toying with the prospect of securing an unprecedented quadruple this season.
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Coutinho, by contrast, has been forced to move to Villa on loan as a means of salvaging his career. Barcelona paid an eyewatering amount for his services around four years ago, even though they didn't seem to have a predetermined plan for how to use him.
Liverpool haven't looked back. In fact, that transfer proved to be somewhat of a watershed moment. It remains as perhaps the best example of the club's recruitment department correctly identifying the biggest areas of need before addressing them.
When Coutinho departed, many expected Klopp to source a replacement for him. It is common practice in English football. Whenever a star leaves, a like-for-like heir has to be chased.
Liverpool have challenged conventional wisdom in recent years and the handling of Coutinho's departure summed up their new-found approach to squad building.
Instead of investing his £146m fee in a replacement offensive player who can essentially do it all, the Reds appreciated the power of their attack without him. Sadio Mane, Mohamed Salah and Roberto Firmino were viewed as capable enough to compensate for his loss, and no additions were required.
Liverpool decided to bolster their defence. In Virgil van Dijk and Alisson Becker, the club used their hefty transfer kitty to sign two expensive but transformational players who would go on to have a significant impact on the future of Klopp's outfit.
Ian Graham, Liverpool's Head of Research, has previously talked about how the club seek improvements in performance, stating: "Say we've got a budget of £50m for transfers, what is the maximum improvement we could get with that transfer budget?"
Once Coutinho's funds were made available, Liverpool determined their defensive department to be their weakest.
After 22 matches of the season, only Manchester City had scored more goals than Klopp's side, but even Burnley had shipped fewer as the Reds placed sixth in the Premier League table for goals conceded.
Not only was Van Dijk one of the best centre-backs around, but he would also offer plenty of value when attacking and defending set-pieces. The Dutchman would secure points almost single-handedly.
Alisson Becker would get his teammates out of trouble by stepping up and dominating one-on-one situations whenever required. His sweeping skills also allowed Klopp's defensive game to be higher and more aggressive. His saves, again, would secure points almost single-handedly.
A number of Liverpool's rivals would have sought a replacement for Coutinho if they had been presented with a similar scenario, but the Reds knew better and they have continued to know better since.
The South American forward has the chance to damage the title hopes of his former teammates on Tuesday night, but his infamous sale in 2018 - and how Liverpool used it - prepared the club to challenge at the summit for the next 10 years.
