Sophie Devine has "full confidence" in the Perth Scorchers' middle order being able to deliver under pressure in the WBBL semi-final against the Melbourne Stars despite their failed attempt to build on the outstanding work of the opening pair against the Adelaide Strikers.

Ultimately it did not cost the Scorchers as their net run rate was far superior to the Sydney Sixers (helped in no small part by the unbroken 140-run opening stand on Saturday) but the way their chase slid after the stand of 118 in 14 overs between Devine and Beth Mooney - needing 42 off 37 balls for victory - to fall three runs short highlighted what could be a telling weakness in a crunch knockout scenario.

Devine (448 runs) and Mooney (524) are far and away the Scorchers' leading batters - and Devine's tally comes with two missed games as well - with the next best being Chloe Piparo's 117 runs in nine innings.

They do have Amy Jones, the England batter, available again after injury but she has been short on time in the middle while Nicole Bolton and Heather Graham - who has a knee injury that makes her a doubt for the semi-final - have struggled for runs and have strike rates under 100.

The two matches Devine missed due to her back injury ended in defeats for the Scorchers, which along with the Strikers game act as a warning sign, although Mathilda Carmichael's two innings earlier in the week (32 off 30 and 35 off 23) suggested she could be worth a spot higher than No. 5.

"We certainly need to learn about our middle order standing up to the job, [but] we back them in 100% to do the job, they are fantastic cricketers," Devine said. "There's equal pressure on everyone when it comes to knockout cricket, it's a clean slate. I think it's a really exciting time…we back our team to do the job in pressure situations.

"If you look at the calibre of players we've got - Amy Jones, Nicole Bolton, Heather Graham who wasn't available today, Chloe Piparo has been outstanding - it's disappointing today, absolutely, but we going to be able to go away and reflect. We have full confidence in our batting from one to eleven, everyone is allowed a bad day every now and then."

Devine and Mooney are in such rich form that they are entirely capable of taking the Scorchers to the title off their own bats. Both players joined from previous clubs in pre-season - Devine from the Strikers and Mooney from the Heat - and Devine is enjoying the combination.

"It's great, she's the world's best batter for good reason," Devine said of Mooney. "For me, it's awesome to have a couple of good partnerships, I think we complement each other well. It's good to be down the other end and she's so calm and controlled with how she plays her innings and it takes a bit of pressure off me."

Devine has not bowled in the two matches since her return but is hopeful of doing so in the semi-final. "That's certainly the plan, today we just didn't want to risk it," she said. "If I had my way I'd probably have bowled four off the long run but taking a cautious approach and hopefully I'll be back at 100%."

Meanwhile, the Stars, who were the first team to book a semi-final spot but fell to defeat at the hands of a spectacular Alyssa Healy century on Sunday, will be waiting anxiously on the fitness of some key players.

Elyse Villani tweaked a hamstring early in her innings against the Sixers, although stayed out in the middle to compile 45 off 28 balls with nine boundaries, and Annabel Sutherland suffered a knock on a finger in the field. Erin Osborne has also been sidelined for the past week.

"We are hoping it's not anything too serious," Nat Sciver said of Villani and Sutherland. "The schedule has been pretty hectic so we've done pretty well with injuries so far."

Sciver was also hopeful there could be an upside to the defeat ahead of knockout matches. "It's a shame not to win, but to be put under that pressure is brilliant practice and hopefully we can keep it a bit under control a bit better," she said.

Devine made it clear she likes nothing more than a winner-takes-all scenario. "I love knockout cricket because everyone starts from scratch and it's game on. It's the best type of cricket to play, puts you under pressure and everything is on the line."