American qualifier Samantha Crawford has stunned former world No.9 Andrea Petkovic to reach the Brisbane International women’s semi-finals.

Crawford, 20, thrashed former French Open semi-finalist Petkovic 6-3 6-0 in less than an hour at Pat Rafter Arena on Thursday.

The world No.142 – ranked 118 places lower than Petkovic – next takes on the winner of Thursday’s Victoria Azarenka-Roberta Vinci quarter-final.

She is the first qualifier to ever reach the Brisbane women’s semis.

Petkovic – a former Brisbane finalist – had no answer for the aggressive Crawford who chanced her arm to pull off winner after winner.

Former US Open junior champion Crawford is in just her sixth main draw WTA appearance yet she is yet to drop a set in the tournament.

It was a crushing blow for Petkovic, 28, who considered giving away tennis after a knee injury capped a tough 2015 in which her mother fell ill.

Earlier, German fourth seed Angelique Kerber became the first woman into the Brisbane semis.

The world No.10 overcame Russian Anastasia Pavlyuchenkova 6-4 6-4.

Former Wimbledon semi-finalist Kerber, 27, plays the winner of Thursday’s Carla Suarez Navarro-Varvara Lepchenko quarter-final.

Kerber is the highest seed still standing in a women’s draw blown wide open by big name withdrawals.

Defending champion Maria Sharapova (forearm) and top seed Simona Halep (Achilles) withdrew earlier in the week.

No.2 seed Garbine Muguruza of Spain was the latest to exit, succumbing to a foot injury trailing American Lepchenko 7-6 (9-7) 1-0 in the second round on Wednesday night.