Concussion shook Sixers' Gardner

Australia and Sydney Sixers allrounder Ashleigh Gardner admits she had been rocked by her third concussion in less than a year, but says she's ready to get back to her best in Thursday's Rebel WBBL clash against the  Brisbane Heat.

The hard-hitting Sydney Sixers' star sat out two WBBL|03 games after copping a ball to the grill of the helmet from English quick Katherine Brunt while playing Perth, after she had mistimed a pull shot.

It was the second time Brunt had the better of her this summer, after Gardner also missed a Commonwealth Bank Women's Ashes one-dayer in October after a similar incident.

The 20-year-old also copped a ball to the head last January in training from regular wicketkeeper Alyssa Healy, adding to the concerns after the Brunt blow in December.

"It definitely did rock me a little bit," Gardner said.

"Obviously, my first one last year was a big thing. It was the first ever time that I've felt that way and obviously, coming off two more this season, I knew what to expect.

"This one was obviously the worst recovery time and missing two games after that wasn't ideal. But my health is more important than cricket."

Gardner played rugby league for eight years growing up, and copped her fair share of knocks.

But none has affected her like the most-recent one.

After hitting 115 from just 52 balls on the opening day of the competition against the Melbourne Stars, Gardner has scored just 44 runs since in four games.

But ahead of Thursday's crunch clash with Brisbane at the SCG, she says she's ready to be back to her best, warning bowlers to target her with the short ball at their peril.

"Teams know now I am susceptible to a short ball," she said.

"But it's a small margin of error for them to bowl short at me. It can either be a wide or (I) connect on it. I don't mind if teams are willing to do that.

"My mindset is where I want to be. I'm playing really well in the nets.

"Obviously, I'm not executing the way I want to in a game but the way that I'm feeling and the positivity I'm feeling, hopefully, it will implement out on the game as well."

The Sixers sit fourth on the WBBL ladder, a win behind Brisbane but only ahead of Perth and the Melbourne Renegades on net run rate, but with a game in hand.

Meanwhile, the Heat have confirmed they will welcome back former Australian allrounder Grace Harris from knee surgery for Thursday's match.

Harris fills the international player slot left vacant when South Africa teenager Laura Wolvaardt returned home to begin university studies.

She was the first player to score a WBBL century in the first edition of the tournament, and after departing the Heat for a season in Renegades red in WBBL|02, Thursday will mark her first match back in teal.

Elsewhere, the table-topping Sydney Thunder have confirmed English representative Fran Wilson will replace Indian allrounder Harmanpreet Kaur in their squad for the remainder of the competition.