Samantha Stosur admits she choked to send China's Zheng Jie through

Australian world number nine Samantha Stosur's horror run at her home Grand Slam continued Wednesday, and she admitted she choked in the final set to hand victory to China's Zheng Jie.

The 2011 US Open champion has never ventured beyond the fourth round in 11 visits to Melbourne Park and she threw away the last five games in a nervy and hard-fought second round clash.

Stosur, who suffered first-round flops at WTA events in Brisbane and Sydney this year, was leading 5-2 in the third but collapsed in front of her home fans and double-faulted to give Zheng victory 6-4, 1-6, 7-5.

"Whatever word you want to put on it, at 5-2 up in the third, double break probably is a bit of a choke, yeah," she said, adding that she was gutted.

"Obviously it's a pretty hard one to take when you get yourself well and truly into a winning position, playing really quite well.

"Then all of a sudden you get to 5-2 and you lose five games straight. It's kind of hard to say much about it right now, to be honest."

Zheng was never going to be a pushover -- she beat Stosur in Sydney last week.

Once ranked 15 in the world with four career singles titles to her name, she has slipped to 40 but had the measure of the Australian in the first set.

Coached by husband Zhang Yu, she executed her favourite backhand shot with precision to rattle the Australian who has long struggled in front of her home crowd.

The first set went with serve until Zheng got the crucial break in the seventh game. Stosur immediately broke back but got broken once again to put the Chinese 5-4 in front and set up a nerve-tingling final game.

Stosur saved seven set points, including one rally of 28 shots, in a game that lasted more than 12 minutes before she sent an easy overhead volley long to hand Zheng the set in 54 minutes.

But cheered on by a boisterous crowd on Rod Laver Arena, Stosur came out for the second set fired up and broke Zheng in the fourth game en route to levelling the match.

Now in her rhythm, Stosur got an early break in the third but Zheng refused to wilt and under pressure, it was the Australian who caved in meekly to miss out on a third round clash with 18th seeded German Julia Goerges.

Stosur admitted her problem was mental, not physical.

"Oh, I think it's 100 percent (mental)," she said. "I think that's what it was. I got tight and then you start missing some balls. You probably think a little bit too much.

"You do it over and over and over again, and then you start not wanting to miss rather than wanting to, you know, make the winner. Instead, it's 'I don't want to make the error'."

Zheng admitted she was amazed she was able to come back in the third.

"I was thinking first time I played on center court is 2006. I thinking, how many times I can play this court? I need to keep fighting and enjoy the match.

"Yeah, (it was) just too simple. It's amazing I can come back."