When Chelsea line up to face Atletico Madrid in the Champions League last 16 on Tuesday, they will be forced to face the ghosts of transfer decisions past.
The Blues will start with Edouard Mendy between the posts, with the world's most expensive goalkeeper, Kepa Arrizabalaga, again forced to watch on from the substitutes' bench.
At the other end will be Jan Oblak, a player so crucial in deciding results that his manager Diego Simeone has likened his impact to Lionel Messi.
For the small matter of just £16 million ($22m), things could have been very different.
Back in the summer of 2018, Chelsea were on the search for a new No.1, with it clear that Thibaut Courtois was on his way out of Stamford Bridge as he edged towards signing for Real Madrid.
The Blues had two players at the top of their shortlist of potential replacements: Alisson Becker and Oblak.
Liverpool won the race for Alisson as the Brazil international swapped Roma for the Reds, leaving Oblak as Chelsea's primary option.
Despite the Blues having an outstanding relationship with the Spanish side, Atleti would not budge when it came to negotiating a deal for Oblak to leave.
The Slovenia shot-stopper had a €100m (£87m/$121m) release clause in his contract, and the Rojiblancos would not be accepting anything less.
Chelsea were unwilling to pay the price; they were set to receive only £35m ($49m) for Courtois as he entered the final year of his contract in west London, and went in search of alternatives.
That search led them to Kepa, almost two years younger than Oblak and, with a release clause of €80m (£71m/$99m), offered more long-term value for money if the potential he had shown at Athletic Club was realised in the Premier League.
It has not worked out and it is fair to ask whether Chelsea did the right thing in turning down the chance to sign Oblak for the sake of an extra £16m ($23m).
While Oblak - who has been courted by two other Premier League clubs in the past - continues to set the standard for goalkeepers around the world, Kepa has spent the past 18 months in and out of the Chelsea team after a string of errors.
The Blues are keen to move the Spain international on, though the fact he still has four years to run on his original seven-year contract makes selling him at a palatable price difficult.
The club were hopeful that during the summer of 2020 a buyer would emerge, and there was some interest from Valencia, albeit in an initial loan deal rather than a permanent transfer.
Last summer, Chelsea knew that even if Kepa did not depart they would need a new permanent No.1, which saw them circle back in Oblak's direction.
In the two years since they first made their interest in him known, the 28-year-old signed a new deal at the Wanda Metropolitano, with his release clause increasing to €120m (£104m/$145m).
While Chelsea were quite happy to spend big in the face of the Covid-19 pandemic, other clubs were not so forthcoming when it came to taking unwanted players off their hands.
As such, and with Atleti again refusing to budge on price, the Blues turned to Mendy at Rennes, who, at £22m ($31m), was more affordable, although an unknown quantity at the highest level.
The Senegal international has certainly been a far more reliable presence than Kepa ever was, though new manager Thomas Tuchel has opened the door to the latter earning more opportunities as he gets his feet under the table at Stamford Bridge.
As for Oblak, he continues to be linked with Europe's biggest clubs, though Atleti maintain their stance that he will not be sold for a penny less than his release clause.
His current contract runs until 2023, though there might be few better places to be than with the Liga leaders right now.
Despite recent slip-ups, Simeone's side remain clear of Real Madrid and Barcelona in the Spanish title race, and are on a far sounder footing, financially, than either of their rivals.
And, with Luis Suarez and Joao Felix combining well in attack, the three-time losing finalists may not have a better chance of finally claiming their first Champions League title this season. As such, Oblak has no reason to think about moving on.
"Now is not the time to speak about transfers," his agent, Miha Mlakar, tells Goal. "Chelsea - Atletico is an important game.
"Chelsea are a new team with a new coach who have made some positive moves, but Atletico is always at their strongest in the most difficult games.
"They showed it against Liverpool last season. Atletico is Atletico and every team must be scared of them."
The daunting prospect of trying to find a way to score past one of the game's best goalkeepers would cause most strikers nightmares.
But if Oblak plays a key role in knocking out Chelsea over the next three weeks, the hierarchy in west London will be having sleepless nights too following the decisions that were made in the summer of 2018.