Madison Keys added to her growing reputation as she breezed through her quarter-final contest at the WTA Family Circle Cup on Friday.

The seventh-seeded 20-year-old blew away fellow American Lauren Davis 6-2 6-2 on the claycourts in Charleston, South Carolina.

Keys routinely pounded serves in excess of 160 kilometres per hour and hit precision groundstrokes for winners.

She hammered four aces, had just one double fault and broke Davis four times.

“I think I was rushing a little bit at the beginning,” Keys said.

“After that I really kind of calmed down and just started playing the right balls, just being a little bit smarter on the court.”

The 21-year-old Davis had stunned top-seeded Canadian star Genie Bouchard in straight sets on Wednesday.

Of the players remaining in the draw none are ranked in the top 10 in the world.

The Australian Open semi-finalist Keys’ next opponent, on Saturday (Sunday AEST), will be Czech qualifier Lucie Hradecka, who upset fourth-seeded former French Open runner-up Sara Errani 6-2 6-4.

The last match of the night saw fifth-seeded Angelique Kerber topple 13th-seeded Irina-Camelia Begu 7-6 (7-3) 7-6 (7-4).

Kerber’s opponent in the semi-finals will be third-seeded Andrea Petkovic, who rallied from a first-set loss to down Danka Kovinic 2-6 6-3 6-1.

Petkovic defeated the Slovak Jana Cepelova in last year’s final.