Mumbai is the only team, which has not opened its account on the points table after back-to-back defeats to defending champions Kolkata Knight Riders, Kings XI Punjab, Rajasthan Royals and Chennai Super Kings.
However, Sammy said they can't take Mumbai for granted.
"In T20, both teams stand good chance. Mumbai has got some match winners. Yeah we can't take them for granted. We need to go out and execute what we have been talking about," he told reporters at the pre-match press conference.
"Over the years when I have played against them (RCB) I have watched them, the more fearlessly they play the better they perform. That is something that the captain (Virat Kohli) has been preaching - go out and play fearless cricket and we are going to do that tomorrow," he added.
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On Australia's inform Mitchell Starc playing tomorrow's match, Sammy said it would be a good addition to the squad if he is available as he has been the most consistent bowler this year in one dayers.
"Yes we are expecting him (Starc) to be in the team tomorrow or as soon as possible. He is decent, and is in good form which always is a plus point. He has had a good year, especially in white ball cricket. So, to have him here to lead the attack would be massive. If he is available tomorrow he would be a good addition to the squad," he said.
Sammy admitted that Gayle is an important player but said everybody's role is as important as any big player in the side.