Madison Keys is enjoying being the underdog after moving into the Australian Open semi-finals on Tuesday.

The American was too good for Czech fourth seed Barbora Krejcikova 6-3 6-2 in their quarter-final, played on a warm day in Melbourne.

Keys reached her fifth career grand slam semi-final, but first since the 2018 US Open.

Riding a 10-match winning streak after claiming just 11 victories in all of 2021, Keys is staying focused as her run continues in Australia.

"I honestly feel pretty neutral, to be completely honest with you. I have gone into every match thinking I can absolutely win any match that I'm out on the court," she said.

"I will say it's been kind of nice to be the underdog for the first time in a long time.

"It's really just not even in my head about winning and losing. It's really just going out, competing, trying to do what the game plan is.

"If that's not working going to Plan B. The rest is kind of not even getting into my brain."

The heat on Rod Laver Arena seemed to get to Krejcikova, the French Open champion taking a medical timeout late in the first set.

Krejcikova said she would learn a lot from her run after struggling with the heat on Tuesday.

"Today it was the heat with some physical conditions that started to bother me during after five games. I mean, from there on, you know, I just couldn't put it together," she said.

"Just still I didn't want to end it up. I wanted to finish match. I wanted to try to do my best. Yeah, I wasn't really able to do that. Still I think it's a really good experience and I can learn a lot from it."

Keys will play either Ash Barty or Jessica Pegula in the last four.