Heather Watson was knocked out of the Hobart International by Tsvetana Pironkova of Bulgaria despite holding match points.
The British number three, 19, served for the match at 5-4 in the third set but lost 7-6 (12-10) 3-6 7-6 (7-2).
It was Watson's fourth match of the week after she came through qualifying.
"Gutted I lost such a close one but I have had four good matches this week and definitely feel that I'm ready for Melbourne," Watson wrote on Facebook.
British number one Elena Baltacha lost to Irina-Camelia Begu in the first round in Hobart on Sunday and is ranked 53 this week, while Anne Keothavong, who lost in qualifying in Sydney, is number 75 in the world.
All three will compete at the Australian Open, which begins with qualifying on Wednesday before the main draw gets under way on Sunday.
Australia's US Open champion Sam Stosur suffered another blow to her preparations as she lost 6-2 6-4 in one hour and 28 minutes to Francesca Schiavone in Sydney.
Stosur, who made an early exit in Brisbane last week, has made 11 appearances at the Australian Open without getting past the fourth round.
"That's what makes the loss so difficult, Melbourne is coming up and I want to start playing well," she said. "I think today I certainly didn't handle that [expectation] side of things at all well.
"I think being in Australia and playing in Australia, I want to play the best I can play and do it all here this month, right here right now.
"When it doesn't happen, it's obviously disappointing. It probably makes it more disappointing here than anywhere else."