From Turf Moor - Chelsea have lost some big names over the years - Eden Hazard, Mohamed Salah, Kevin De Bruyne and even Jose Mourinho - but they could be about to suffer one of their biggest losses ever.
No, this is not about departing owner Roman Abramovich, but instead central defender Antonio Rudiger.
The 29-year-old hasn't always been a star at Stamford Bridge, let alone in the Premier League. But over the past year to 18 months, his stock in West London has risen exponentially - to the point where every major European club is queueing up to land him on a free transfer once his contract expires this summer.
Rudiger has been in talks over a new deal for the best part of two years but Chelsea haven't been able to get him to commit. Indeed, it's believed that the German feels as if he has been disrespected in some way, and it's going to take a huge change in stance from the club to persuade him to prolong his tenure.
At Turf Moor, during Chelsea's comprehensive 4-0 spanking of Burnley, Rudiger showed why the club should be doing everything in their power to keep him.
Simply put, he was faultless.
Only last Sunday Rudiger was stifling and nullifying the huge threat of Mohamed Salah in the Carabao Cup final, and this weekend he was keeping quiet the imposing powerhouse that is Wout Weghorst. A completely different kind of threat but a threat nevertheless.
That, in a nutshell, is the beauty of Rudiger - he is a man for all occasions, capable of marking any leading player in world football. Small, nippy and technically brilliant or big, strong and powerful, it really doesn't matter to him.
His manager Thomas Tuchel knows his importance, too, though the former PSG and Borussia Dortmund boss acknowledged that the impending departure of Abramovich is unlikely to help Chelsea turn around negotiations with Rudiger.
“Maybe the bottom line is we cannot help it; it’s what it is,” Tuchel said of things not panning out so far. “And you never know, maybe there’s a positive effect on the negotiation, maybe there’s a negative effect.”
“We cannot predict and I would like not to predict, not to start predicting all scenarios, because we just lose focus on it. But of course everybody has a different situation, everybody feels differently about it.”
The irritating thing for Chelsea, and their supporters, is that they've hand plenty of time to address Rudiger's contract and sort out an extension.
In the past they have lost the likes of the aforementioned Salah and De Bruyne, but at the time they departed they weren't at the level Rudiger is at. Losing players at their peak is something that doesn't usually happen under Abramovich's watch.
You could argue Eden Hazard fits that bill but even his departure was different - Chelsea allowed him to leave because of the insane money Real Madrid were offering, whereas Rudiger, as it stands, is choosing to leave of his own volition.
At Turf Moor, Rudiger not only dealt with Weghorst with consummate ease, he also bailed out the desperately disappointing Saul Niguez in his duel with Aaron Lennon. The less said about the Spaniard's inept performance at left wing-back the better.
He even poured forward with the ball at his feet, operating as a supporting wide centre-back, and flashed a couple of brilliant strikes at goal to test England goalkeeper Nick Pope.
For Chelsea's sake, they had better hope that scouts of Real Madrid, Barcelona, Bayern Munich and co were not in attendance. If they were, they will have seen the perfect showcase of what Rudiger has to offer, even if it was against a side who are struggling to stave off relegation.
It's been a tough week for Chelsea, with defeat in the cup final and doubt over their ongoing ownership, but it's actually been a superb week for Rudiger individually.
He has reaffirmed his status as one of the best centre-backs in the world, and if there's an even a 1% chance of keeping him, Chelsea must keep pushing like they have never pushed before.