Chelsea's current offer remains short of Sevilla's valuation of centre-back Jules Kounde, 90min understands.
Kounde is a long-term target for the west London club, coming very close to a move to Stamford Bridge last summer before the deal collapsed.
This year, the 23-year-old forms part of Chelsea's plans to rebuild the backline following the departures of Andreas Christensen and Antonio Rudiger at the end of their respective contracts. Kalidou Koulibaly has already joined from Napoli for £34m, but head coach Thomas Tuchel wants to add two central defenders to his squad.
90min understands Chelsea's current €55m (£46.8m) offer falls short of Sevilla's €65m (£55.4m) valuation and was swiftly knocked by by the Spanish club - but they are still in talks, and sources have indicated that they are confident of finally landing the French star.
Chelsea had the opportunity to sign the France international for around €60m in late June, but at the time they were prioritising a move for Juventus' Matthijs de Ligt - who now appears destined for Bayern Munich - and a deadline set by Sevilla passed.
While new Chelsea owner Todd Boehly has pursued other targets at the behest of Tuchel, including Koulibaly, De Ligt and Paris Saint-Germain's Presnel Kimpembe, interest in Kounde has never waned. Indeed, Boehly has held talks with Sevillia sporting director Monchi - although the Blues do face competition from big-spending Barcelona.
The Blaugrana are keen to include at least one player in the deal in part-exchange, although it remains to be seen whether that is something Sevilla would accept.
Sources have confirmed to 90min that both sides are in talks over the France international but neither has agreed a fee, with his current employer holding out for around €65m and hopeful that a bidding war will eventually see their valuation met.
Both Chelsea and Barcelona already have broad agreements in place with Kounde over personal terms. A move to the Premier League had originally been the defender's preference, although his representatives have been irked by how slowly things have moved and it is now in the balance.
Meanwhile, the west Londoners' offer for Kimpembe is still on the table, but the 26-year-old has reservations about leaving PSG - especially with Milan Skriniar's move from Inter stalling.
90min understands that RB Leipzig's Josko Gvardiol and Pau Torres of Villarreal have also recently moved back onto Chelsea's radar as they continue their extensive search for new centre-backs.