Ba, 31, had netted 14 goals in 18 appearances for Shanghai Shenhua this season but appeared to badly break his leg in a tangle with a Shanghai SIPG FC defender.
The Senegal international was taken off on 70 minutes as Fredy Guarin’s late penalty saw Shenhua pick up a 2-1 win after almost 10 minutes of injury time which included the sending off of Jiajie Wang.
The Premier League club tweeted: “All at Chelsea FC send our best wishes to former striker @dembabafoot. Get well soon Demba.”
“It could end Ba’s professional career. I would rather lose the game than lose Ba. God is unfair. Ba is too good to have this happened to him.”