Besiktas are in talks with Chelsea over a January move for an unnamed player, according to the Turkish's side's club president.
The Blues have already sanctioned a string of loan deals for members of their Under-21 ranks in January but the futures of the fringe members of their first team remain under scrutiny.
Germany international Andre Schurrle, goalkeeper Petr Cech and winger Mohamed Salah in particular have struggled for opportunities in Jose Mourinho's first team this season and have inevitably been linked with January moves.
The Evening Standard suggests it is former Basel star Salah, along with Dutch youngster Nathan Ake, who Besiktas are in discussions over, although president Fikret Orman is reluctant to reveal who it is out of fear of the deal being scuppered.
"I was in England and held talks with Chelsea but it would be wrong to disclose who the negotiations were regarding," Orman said.
"The talks are ongoing, if I was to tell you who the transfer was regarding it could make the move more difficult."
Chelsea have already sanctioned a number of temporary moves for their youth players this month. Promising midfielder Lewis Baker has joined Sheffield Wednesday, while full-back Todd Kane has joined Nottingham Forest until the end of the season.
John Swift has joined Swindon Town, Alex Kiwomya has linked up with League One rivals Barnsley, while Patrick Bamford and Alex Davey have renewed their deals at Middlesbrough and Scunthorpe United respectively.
Tomas Kalas has also recently joined Bamford at the Riverside Stadium while Nathaniel Chalobah and Islam Feruz are expected to secure temporary moves in the coming weeks.
But Mourinho has maintained throughout the season that no members of his first-team squad will leave, with no additions to be made either.
In late December, the Chelsea boss said: "We can't lose players for a long period of time, but our project is to start and finish the season with the same group of players, so there will be nobody to leave and nobody to come in either."