Warner's axing comes a day after he claimed "full responsibility" for the side's latest defeat to the Chennai Super Kings.
He scored 55 from 57 balls at the top of the order before Williamson and Manish Pandey scored quick runs as the Sunrisers made 171 for three, which Chennai chased down with nine balls remaining.
"I take full responsibility. The way that I batted was obviously very slow," Warner told host broadcaster Star Sports after defeat.
"I was hitting a lot of fielders and [was] very, very frustrated... Look I take full responsibility from a batting point of view. I felt [that with] Manish coming back into the team, the way that he batted was exceptional. And obviously Kane [Williamson] and Kedar [Jadhav] towards the back end there, they put some boundaries away and got us to a respectable total. I felt that we were probably just below par from where we were. But yeah look, at the end of the day, I'll take full responsibility."