Anuj Rawat (48 off 25) and Dinesh Karthik (38 not out off 26) shared a 95-run stand off 57 balls for the sixth wicket to give some respectability to the total.
Virat Kohli, who opened alongside du Plessis, made 21 off 20 in his first competitive game in more than two months.
Mustafizur Rahman was the stand out bowler for CSK taking four wickets. Brief scores: RCB in 20 overs (Anuj Rawat 48, Dinesh Karthik 38 not out; Mustafizur Rahman 4/29).