Ba has a £7million release clause in his contract which becomes active when the transfer window re-opens.
The striker has shown some excellent form this season and already has 13 goals to his name this term.
This has seen a host of clubs linked with a possible move, including Arsenal, Tottenham, QPR and French giants Paris Saint Germain.
Now Chelsea are reported to have moved into pole position after Sky Sports sources confirmed talks were due to take place between Ba's representatives and the European champions on Sunday.
Chelsea manager Rafa Benitez refused to be drawn on reports linking the Senegal striker, 27, with a move to west London.
Speaking after the 2-1 win at Everton, he said: "We don't talk about this business, we had a very important game today."