They could lose one Hazard this summer, but could Chelsea bring another one back to the club?
Thorgan Hazard has had an excellent Bundesliga campaign for Borussia Monchengladbach, netting 12 times and with another nine assists to his name, while also scoring twice for Belgium in the Nations League.
Just like Eden, Thorgan was once a Chelsea player from 2012 to 2015, but it looks like the Blues might have let another good prospect slip through their fingers, along with Mohamed Salah and Kevin De Bruyne.
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Although the Belgian didn't make a single appearance in his three years in west London, he has been tipped to return to SW6 for a very long time with reports of the Blues having a buy-back clause inserted into the deal that saw him depart.
And Borussia Monchengladbach sporting director Max Eberl has admitted the 26-year-old wants to leave this summer.
He said: "Thorgan has informed us that he doesn't want to extend his contract and that he wants to leave the club in the summer to take the next step. I've heard this statement 15 times in the last 10 years as really great players have left us. That's the way it is for us."
However, the exact details of the contract were far from clear.
Speaking in 2016, Eberl dismissed the idea of such a clause being in place.
"There is no clause," he told Express.de. "I do not want to comment on any contract content. But we also do not need to make any secrets about it.
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"If we get such a top player from Chelsea, then Chelsea has, of course, always the opportunity, in whatever form, to think about this player."
In February, Sport Witness translated a report by SportsBILD that claimed that Chelsea have a right to match an offer if another club come in for Thorgan Hazard, rather than a straight buy-back clause.
"To be honest, even I don't know if there is one," said Thorgan in an interview with Onze Mondial.
"My father [Thierry Hazard] deals with that now. Sometimes, I hear there is one. Here, I'm told there isn't. Frankly, I don't know.
"It's not that I don't care, but I don't think about it. I'm happy here. If Chelsea want to buy me back one day, I think they'll do it, that's not an issue. Actually, if there is or isn't one, it's the same, really.
"If Chelsea want me, they'll pay for my transfer and they'll take me back. It's just a detail."
With the 25-year-old even unsure if Chelsea have a clause to re-sign him, German publication Bild stated that Maurizio Sarri's side can indeed buy him back.
'I wish him all the best' - Gonzalo Higuain comments on Eden Hazard to Real Madrid transfer rumoursThey claim that the FA Cup holders have a clause but it is only valid for the 2019 summer transfer window.
That becomes another issue as the Blues are in the midst of a transfer ban. FIFA have ruled that Chelsea cannot register new players for the next two transfer windows, which would mean this summer and January 2020.
However, the Blues are going to the Court of Arbitration for Sport to try to get the ban reversed, or at least get it frozen until the appeals process takes its course.
If Eden makes the move to Real Madrid this summer, then it will only be third brother Kylian who will be left at Chelsea, however the younger brother is currently on loan at Cercle Brugge.
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