What happened last week doesn't mean anything today as the Zheng-Stosur battle remains unpredictable, said Aussies coach.

Des Tyson, Australian national junior coach, has always kept a close eye on Chinese ace Zheng Jie since instructing her in the nation's youth camp in early 1990.

The 47-year-old, who also oversaw local favorite Samantha Stosur for a while, knows her up-and-down emotional game could be an issue.

So he's the right person to make a comment on the duo's six clashes at the Rod Laver Arena.

"It's a tough match. They played a number of times. Sam is wining 3-2, Zheng won last week. It's not easy for Sam, Zheng reminds me a bit of Lleyton (Hewitt), running well on the court and making the most of her talent and ability.

"One thing for sure, Sam has to bring out her A game to beat Zheng. Zheng is very consistent while Sam can be up and down. If Sam not playing well, I can see Zheng winning again. We have to wait and see. It's 50-50 for me.

"Technically, Sam has to dominate the points a little bit more, taking the control earlier. Be more aggressive with returning and runs Zheng a lot. Once Zheng gets established in the rally after three or four balls, the chance is Zheng will win. Sam has to win the points fast in the first several shots, otherwise she struggles."