Chelsea's hold over Thibaut Courtois is looking more precarious than ever and the speculation over his future as he edges toward the final year of his contract, which expires in June 2019, is likely to overshadow the rest of this season.
Last week, the goalkeeper laid out in full the family situation that pulls him toward Spain despite his general satisfaction with life at Stamford Bridge. Real Madrid are long-term admirers of his talents and Chelsea's appeal will ultimately count for nothing if he decides he wants to be closer to his two children.
There does at least appear to be more stability in front of Courtois, where Andreas Christensen has already done enough this season to suggest he can be the elegant centerpiece of Chelsea's defence for the next 10 years. Christensen's emergence has not been a total surprise; he returned to Stamford Bridge last summer as the most polished product of the loan system since Courtois, having enjoyed two full seasons of Bundesliga and Champions League football with Borussia Monchengladbach.
Both he and Courtois benefited from spending multiple years on loan with the same club, unlike the vast majority of the players in Chelsea's controversial mass loan system. Rather than having to adapt to new countries, cultures and teammates each season, they were able to settle into a productive, stable environment over a longer period and focus entirely on honing their skills.
Meanwhile, their loan clubs felt more incentive to invest in their development in the knowledge that they were not simply passing through. Courtois was allowed room to grow into a key figure on the pitch and in the dressing room by Atletico Madrid coach Diego Simeone, while 'Gladbach sporting director Max Eberl mounted a public campaign to try to convince Chelsea to sell Christensen once his ability and potential became clear.
By the time Courtois began his Chelsea career in the summer of 2014, he was regarded as one of the top five goalkeepers in the world and ready to put an end to Petr Cech's career at Stamford Bridge. Christensen may not be quite that polished yet, but he is already threatening to do the same to David Luiz.
With such spectacular results in these two cases, it's tempting to ask why Chelsea wouldn't engage in more multiyear loan agreements for their best young prospects. Often in recent years, such arrangements have been struck simply as a convenient way to get rid of unwanted talent, such as Fernando Torres to Milan in 2014 or Juan Cuadrado to Juventus in 2016. The counterargument, however, is that it is very rare to find a club that is stable and successful and also happens to be interested in developing another club's youngster.
Atletico took Courtois in 2011 because they saw an opportunity to acquire an elite replacement for the Manchester United-bound David De Gea for a fraction of the price. Most of the time, the stars do not align so well. Courtois and Atletico also highlights an unusual potential pitfall of the multiyear loan agreement: the danger that an elite young prospect could "go native," forming lasting attachments during his time on loan that cause problems for him and his parent club later.
Christensen enjoyed his time in Monchengladbach, making friends and growing up off the field as well as on it, but there was nothing to keep him in Germany when it was time to return to Chelsea. His girlfriend had travelled over with him and England had been his home since the age of 16. Madrid, however, resonated on a deeper level with Courtois immediately.
"From the first minute, I fell in love with Spain: the people, the way of life, the food," he told Spanish newspaper Marca in September 2016. "I have kept up the late dinners, the siesta, and most of the television I watch is Spanish.
"I consider myself half-Spanish... when I left Spain, I had it very clear in my mind that I would return one day."
It is this connection, reinforced by the birth of his two children with ex-girlfriend Marta Dominguez, that Chelsea have been battling against with Courtois from day one. This is no small irony given that they have benefited more than anyone from the three years in Madrid that formed him as a player as well as a person.
Regardless of whether the current uncertainty is resolved by a bumper new contract or a big-money move to Real Madrid, Courtois will be held up alongside Christensen as a shining success of Chelsea's development strategy. He has already justified the decision to jettison Cech by providing the foundation for two Premier League title-winning teams in three seasons, even if his own era between the Stamford Bridge post does not prove anywhere near as long as was once hoped.
If he does end up following his heart and his family back to Spain next summer, though, the story of Courtois will also be a reminder that outsourcing a player's development is never a perfect science, even when it works perfectly.