Baptist, ranked 45th on the WTA list (33rd as of Monday), put up strong resistance against the Belarusian, but buckled under pressure in the finals of the first and second sets.
There were no breaks in the first set until 5:4, when the reigning champion broke her rivals' serve.
The world number one broke for 4:2 in the second half of the game, but Baptist came back quickly and tied it at 4:4. However, Sabalenka broke again in the 10th game, in which the American made three double faults in a row and almost gave the victory to her opponent.
Sabalenka will play Elena Rybakina in the semifinals, who earlier knocked out Jessica Pegula with a three-set upset (2:6, 6:3, 6:4).
The Belarusian and Kazakh are 1-1 this year. Rybakina won her match in the Australian Open final, and Sabalenka got her revenge in the Indian Wells final.
"I think it's going to be another real battle. It's always a real fight and a big challenge to play with Elena. I think we push each other to the limit. We just bring good tennis. I definitely think it's a pleasure for you to watch us and I'm really excited to meet again," Sabalenka said before the duel with Rybakina.
In the second semi-final, Coco Gauff and Karolina Muchova will clash.
