Samuel Eto'o had earlier scored a hat-trick for the Blues, and Mourinho has hinted that he would rotate the Cameroonian with Ba in the next few matches.
"It's time for Demba. It's a pity because Nando is in a good moment, but it's time for Demba," PA quotes Mourinho as saying.
"Demba had a fantastic week, [it was] very difficult for me to leave him out of selection because he worked very, very well. Next matches is for Demba or Samuel. Let's go."
Chelsea, who moved to within two points of leaders Arsenal with the win, will face Stoke City in the FA Cup next Sunday.