Home hopes Zoe Hives and Kimberly Birrell have parlayed Australian Open wildcard entries into the most significant wins of their fledgling careers.

Hives defied her ranking of No.225 in the world to upstage seasoned American Bethanie Mattek-Sands 6-1 6-2 before Birrell joined her in the second round with a 6-4 6-2 defeat of Spanish qualifier Paula Badosa Gibert.

Hives, a 22-year-old from Ballarat making her grand slam main-draw debut earned a crack on Wednesday at French 19th seed Carolina Garcia, while Birrell will play Croatian Donna Vekic.

Hailing from the same Southport tennis centre that produced Samantha Stosur and Bernard Tomic, Birrell is enjoying a breakout summer.

After winning last month’s Open wildcard playoff at Melbourne Park, the 20-year-old stunned world No.10 Daria Kasatkina at the season-opening Brisbane International before also reaching the second round last week in Sydney.

Like Hives, Birrell can look forward to a nice rankings rise following their big breakthroughs, not to mention a career pay day of at least $85,000.

Hives and Birrell join West Australian qualifier Astra Sharma as first-time main-draw winners at the Open.

Sharma earlier on Monday outlasted wildcard Priscilla Hon 7-5 4-6 6-1 in a gruelling all-Australian affair on Court 7.

Hon needed medical assistance after the two-hour-and-nine-minute encounter played in oppressive heat.

Hives, Birrell, Sharma and Hon are among 14 Australians in action on day one.