Surprise strategic shift for Jonassen's elevation explained

Thursday's thrilling World Cup semi-final tossed up more twists than Jess Jonassen does off-breaks but it was the Queenslander who was the centre of perhaps the biggest surprise of the night.

Following the wicket of Beth Mooney for 28, Australia's score was 2-68 as Jonassen walked through the electronic advertising signage out to the middle of the Sydney Cricket Ground to the shock of fans, former players and members of the press.

It was just the second time the 27-year-old had batted at this World Cup after making two in the tournament opener against India, and the experiment lasted just three balls as Jonassen holed out to long-on for one from the spin bowling of South Africa's Nonkululeko Mlaba.

Fortunately for Australia, captain Meg Lanning scored a match-winning 49 in her side's tense five-run rain-affected win over the Proteas to advance to the final on Sunday.

Speaking after the victory, Lanning said Jonassen's promotion was an extension of their tactic of having a left-hander and right-hander at the crease where possible while also trying to fill the enormous hole left by the injured Ellyse Perry.

"We put 'JJ' (Jonassen) up to lengthen the line-up a little bit," Lanning explained. "Obviously we've lost 'Pez' (Perry) so we had to think outside the square a little bit.

"She's a good player of pace bowling and that's what they were doing at the time.

"They were chopping and changing between spin but we felt even against their left-arm orthodox left-handers were a good match-up so we thought she could go up there and play a role for us.

"It didn't come off for us today but that's the great thing about our team, we're able to try different things and sometimes they work, sometimes they don't."

While Jonassen's ascension up the order surprised those off the field, it did not surprise Proteas captain Dane van Niekerk marshalling her troops in the middle.

Van Niekerk has watched Australia re-jig their batting line-up during the tournament, replacing right-handers with right-handers, left-handers with left-handers.

And when it was Jonassen strolling out to the centre instead of hard-hitting veteran Rachael Haynes, South Africa's skipper and Sydney Sixers allrounder knew exactly what the Brisbane Heat champion is capable of.

In two separate meetings across two Rebel WBBL seasons in 2018, Jonassen hit van Niekerk's leg-spinners for six and the Proteas captain was glad a third was not struck last night.

"I wasn't surprised," van Niekerk said.

"I think she's a very good batter. She was brilliant in the Big Bash with the bat and the ball.

"We didn't take her lightly when she came in. She's cleared the boundary off my bowling a couple of times.

"I knew the way they juggle their left, right, let, right combination. We spoke about it in our team meeting. The team was ready.

"We didn't think two right-handers would be in the middle for a long period of time."

Whether Jonassen retains her position in the middle order for the final against India remains to be seen, but having finished the WBBL05 season as the eighth-leading run-scorer, Jonassen is a handy option for Lanning and the Australians should an opportunity present itself once more.