This summer, Chelsea were left reeling at their decision not to insert a buy-back clause when they sold Romelu Lukaku to Everton. Antonio Conte was keen to buy the Belgian striker but found his route blocked after the Toffees demanded £70million for his signature.
But it appears the money men at Stamford Bridge do not make the same mistake twice, at least with regards to another Belgian star. Thorgan Hazard, brother to Eden, could become the latest player embroiled in a buy-back saga.
A loan spell with Borussia Monchengladbach led to a permanent deal in January 2015 and the Blues made a tidy profit in the process. They generated €8m from his sale, making €7.5m on the €500,000 fee they paid in July 2012.
Even that inflated fee is proving a bargain for the Bundesliga outfit. The 23-year-old scored twice in Gladbach's recent 4-1 thrashing of Werder Bremen and was named man of the match by Kicker magazine as a result.
In fact, so impressive has Hazard been that there is now concern that Chelsea will look exercise their right bring him back to west London. Germany newspaper Bild claim that the Blues would have to pay just €15m to re-sign him.
On current form, he is certainly worth more than that but getting him back in a blue shirt is far from straightforward. For starters, the agreement is set to expire at the end of the year, leaving Antonio Conte with just 14 weeks to make a decision on the winger.
Secondly, the player himself seems perfectly content at his current club, telling reporters that he has no interest in talking about rejoining Chelsea.
Hazard told reporters: "I've signed a long-term deal and I am only focused on Borussia. I feel good here, and am currently not thinking about any other club."
For Chelsea, the most likely option could be to broker a deal for Gladbach that would see the clause invalidated. The German club would have to pay a hefty fee to do that but if it means keeping a player who has six goals in just seven appearances this season, it could be a price worth paying.
What Chelsea will be keen to avoid is a repeat of the Kevin De Bruyne situation. The playmaker left for Wolfsburg in a £17m deal in 2014 only to return to the Premier League for £55m after a stellar 18 months in Germany.
There is little to suggest that Hazard can reach De Bruyne's level but should he continue to flourish, Chelsea fans and critics alike will start to wonder exactly why he was allowed to leave in the first place.