Chelsea have made a serious approach for Marseille defender Cesar Azpilicueta, the French club have confirmed.
The Blues have allowed Jose Bosingwa leave the club this summer and are looking to add to their defensive line up ahead of the new season.
And Chelsea, having already made three attacking recruits this summer, have made an enquiry as to Azpilicueta's availability.
"Chelsea have made a serious approach for Cesar," Marseille president Vincent Labrune said.
Roberto Di Matteo has already brought in Marko Marin, Eden Hazard and Oscar ahead of the new season, as the Italian attempts to breathe new life into his midfield.
Meanwhile, Wigan Athletic chairman Dave Whelan says Chelsea can sign winger Victor Moses, but only for the right price.
Moses has been heavily linked with a move to west London, having assisted in Wigan's Premier League survival.
And Whelan, never one to stand in the way of his players' ambition, says he will allow Moses to leave should Chelsea present an acceptable offer.
"I have spoken to Chelsea's chief executive and they are easy to deal with. We have told them the price and they will come back and agree it or not," said Whelan.
"We would much prefer the player to sign a new contract and stay but he wants to go to Chelsea and it's a good club so we cannot stand in his way."
With Didier Drogba having left for Shanghai Shenhua after failing to agree a new deal, Moses is likely to provide an extra attacking option, alongside Fernando Torres.
Daniel Sturridge, Ryan Bertrand, Oriol Romeu and Juan Mata have returned to training with Chelsea after their London 2012 campaign in the Olympic football competition.
Following Spain's exit from the group stage and Team GB's exit in the quarter-final, the quartet have returned to training with the Stamford Bridge club, ahead of the Community Shield against Manchester City on Sunday.