Australian Open champion Sabalenka will rise to the top of the WTA rankings when they are updated after the tournament and was playing with the confidence of a world number one as she pounded Kasatkina with 31 winners.
Kasatkina lost in straight sets to the Belarusian last month in Cincinnati and had clearly not cracked the code, as Sabalenka overwhelmed her at every turn.
"I think I'm playing great tennis," Sabalenka told reporters. "But there is always things to improve. There is always things to keep building and keep getting better with every match you play."
Sabalenka next faces China's Zheng Qinwen, who knocked out 2022 finalist Ons Jabeur in straight sets.
The second seed said her opponent will have nothing to lose in their first meeting.
"She played great tennis against Ons. I haven't watched her previous matches," Sabalenka said.
"The trickiest part is that she's moving well, playing some heavy shots. I have to be physically and mentally ready that it's going to be some winners against me in that match.
"I just have to focus on myself more than on her, on my game. I know if I'll bring my tennis there, I have chance to win this match."
The players traded breaks early in the first set before Sabalenka wrested the lead, breaking Kasatkina to love thanks to a series of aggressive forehand shots in the fourth game.
Kasatkina had struggled with double faults through the first three rounds and they were a problem yet again on Monday, as she handed Sabalenka a break with a double fault in the sixth game and in the opening game of the second set.
The Russian broke back in the second game, as Sabalenka put up a pair of unforced errors and a double fault herself, but Kasatkina's momentum was short-lived as the Belarusian converted on a break point to retake the lead in the third game.
The players swapped breaks yet again late in the second set before Sabalenka forced Kasatkina into a backhand error to break her serve on match point and pumped her fist with satisfaction.
