The South African opener provided a solid foundation with a well-paced fifty, Scored 81 runs off 56 balls.
The wicket-keeper finished the innings with a flourish, smashing five sixes in his 40 Runs of 21-ball knock
Young pacer Mayank Yadav picked up 3 crucial wickets for just 14 runs, derailing RCB's chase.
LSG openers started well, reaching 54 runs in the powerplay overs.
Virat Kohli showed glimpses of form with a 22-run knock but was dismissed by Siddharth.
Glenn Maxwell was the most successful RCB bowler, taking 2/23 in his four overs.
RCB lost key wickets early, including Faf du Plessis (run-out), Glenn Maxwell, and Cameron Green, leaving them struggling at 58/4.
Manimaran Siddharth and Krunal Pandya's early spin attack surprised RCB batsmen.
Mahipal Lomror's quickfire 33 runs off 13 balls offered RCB a glimmer of hope.