The Premier League side are stepping up their summer transfer efforts after completing a deal to sign Raheem Sterling from Manchester City earlier this week.
With Antonio Rudiger and Andreas Christensen leaving at the end of last term, a focus for manager Thomas Tuchel has been signing new defenders with one deal moving closer.
Chelsea are confident that they will be able to get a deal for Kalidou Koulibaly over the line, with the 31-year-old likely to head for Stamford Bridge in the coming days.
Tuchel's side had been looking for a deal to sign Nathan Ake from Man City, however that collapsed when the two sides failed to agree a transfer fee, but according to talkSPORT's transfer man Alex Crook, that hasn't slowed the club down in the transfer market.
Speaking on White and Jordan, Crook said: "Chelsea are still on the hunt for two more central defenders.
"One of them could be Presnel Kimpembe from Paris Saint-Germain, although the clubs are yet to agree a fee.
"Keep an eye on long-term target Jules Kounde, and I've also been told that Dayot Upamecano is also being discussed at Stamford Bridge.
"That could have a domino effect if Mathijs de Ligt completes his move to Bayern Munich.
"A bit of a blow to Chelsea who thought that this Nathan Ake deal was done."