The former Manchester City striker is known to be unimpressed with the lack of investment in the squad since he joined for around €22 million in January of last year, even though Kaka was brought back from Real Madrid during the summer and Keisuke Honda and Adil Rami have been recruited this winter.
The striker's agent, Mino Raiola, has alerted clubs to his client's situation as they explore the player's options - and Chelsea manager Jose Mourinho, keen on bolstering his striker options during January, has asked to be kept informed of the situation.
The Blues were keen on making a move for Wayne Rooney during the summer only to be met with resistance from Manchester United, while they have also been linked with a move for Napoli's Gonzalo Higuain in recent days - though Mourinho played down talk of a deal for the Argentine to reporters on Friday.