Chelsea are making a late attempt to sign Atletico Madrid and Spain midfielder Saul Niguez.
The 26-year-old was a key player as Atletico won La Liga last term, making 33 appearances.
Chelsea had thought a deal for Saul improbable but there is now confidence that a transfer can be concluded, probably on loan.
Sevilla earlier confirmed that they had rejected Chelsea’s “unsatisfactory” offer for France defender Jules Kounde.
The Spanish club are standing firm over the fee required for Kounde, insisting he will not be allowed to join the Blues for less than his 80m euros release clause.
Sevilla sporting director Monchi said in a press conference a bid had been rejected for the 22-year-old.
“The only formal offer from Chelsea came last Wednesday,” he said.
“We weren’t satisfied with the offer, and it was linked to Chelsea selling a player. It was a decent fee but it didn’t meet our criteria.
“We haven’t spoken with Chelsea since Friday night.”
The Blues have been heavily linked with Kounde this summer and were hopeful a deal could be reached following Kurt Zouma’s move to West Ham.
Kounde, who joined Sevilla in 2019, has made 91 appearances for the club and attracted the attention of many of Europe’s top clubs.
“There’s been a lot of talk about moves made for Jules, the majority of which were rejected by the player,” added Monchi.
“If there was one club he liked the look of, it was Chelsea.”
Chelsea must now meet the release clause – or submit an offer acceptable to Sevilla – if a deal is to be completed before the transfer deadline on Tuesday.