Having already snapped up Raheem Sterling in a surprise deal, the Blues shifted their focus to filling the hole that will be left by the departing Antonio Rudiger.
The German giant was colossal at the heart of the Chelsea rearguard all season long and his departure will come as a massive blow to the west London side.
However, in Koulibaly, they might just have got their hands on a ready-made replacement.
The Senegalese man-mountain has been turning the heads of the European elite for many a season now and barely a transfer window has gone by without him being linked to one of the many continental superpowers.
Now, it seems like Chelsea have won the race, with Sky Sports reporting that Koulibaly will sign on the dotted line for a cushy deal believed to be worth around £160,000 per week.
That deal will make the Senegalese one of the highest-paid centre-backs in the Premier League, but where exactly will he rank in the defensive money game?
Well, thanks to data from Spotrac, we can reveal that Koulibaly’s deal will make him the fifth highest-paid centre-back in the English top flight.
You can check out the top 20, and their weekly wages, in the list below:
The 20 highest-paid centre-back in the Premier League
20. Ben Godfrey, Everton: £77,000
19. Eric Bailly, Manchester United: £80,000
18. Jonny Evans, Leicester City: £80,000
17. Tyrone Mings, Aston Villa: £80,000
16. Pablo Mari, Arsenal: £85,000
15. Nathan Ake, Manchester City: £92,000
14. Joel Matip, Liverpool: £100,000
13. Thiago Silva, Chelsea: £105,000
12. Ruben Dias, Manchester City: £115,000
11. Kurt Zouma, West Ham: £120,000
10. Victor Lindelof, Manchester United: £120,000
9. Aymeric Laporte, Manchester City: £120,000
8. Yerry Mina, Everton: £120,000
7. Malang Sarr, Chelsea: £120,000
6. Ben White, Arsenal: £120,000
5. Kalidou Koulibaly, Chelsea: £160,000
4. Harry Maguire, Manchester United: £189,000
3. Virgil van Dijk, Liverpool: £220,000
2. John Stones, Manchester City: £250,000
1.Raphael Varane, Manchester United: £340,000
Not even close.
Varane, who had a thoroughly forgettable first season in a United shirt, is streaks ahead of the rest of the pack sitting pretty as the highest earning CB.
Seeing the likes of Matip and Thiago Silva ranked so low will undoubtedly come as a surprise, while the presence of Maguire in the top five might leave a bit of a sour taste in the mouths of the Old Trafford faithful.