GRITTY: Karolina Pliskova hits a return to Naomi Osaka
Keys will play defending Brisbane champion Karolina Pliskova in Sunday afternoon's final. Pliskova beat Australian Open champion Naomi Osaka 6-7 (10), 7-6 (3), 6-2 after saving a match point.
Keys said a chat with her coach Juan Todero helped to swing the momentum.
"He pretty much just said 'Don't be discouraged'," Keys said. "I felt like I had chances, but couldn't close on those ... and once I did, I felt the momentum went back and forth but I gained confidence."
Pliskova will attempt to win her third Brisbane title in four years.
Osaka broke for the first time for a 6-5 lead in the second set after winning the first-set tiebreaker. But the Japanese player was not able to convert the break.
"I was proud I stayed with her because it could go a really bad way after that first set," Pliskova said. "There was not many things I did wrong, it was more about her (playing well)."
Despite losing her opening singles match in Brisbane, top-ranked Ash Barty has managed valuable court time on the way to the women's doubles final.
She will partner Kiki Bertens against top-seeded Barbora Strycova and Su-Wei Hsieh on Sunday.
Results
Semifinals
Singles
Madison Keys (USA x8) bt Petra Kvitova (CZE x6) 3-6, 6-2, 6-3
Karolina Pliskova (CZE x2) bt Naomi Osaka (JPN x3) 6-7 (10/12), 7-6 (7/3), 6-2
Doubles
Hsieh Su-Wei (TPE)/Barbora Strycova (CZE x1) bt Lyudmyla Kichenok (UKR)/Yang Zhaoxuan (CHN) 7-6 (7/3), 6-3