Western Storm missed the chance to cement a spot in the Kia Super League final after their nine-wicket thrashing by Loughborough Lightning at Edgbaston.
Defending champions Storm are assured of a spot at Finals Day at Hove on August 27, with their six wins to date guaranteeing a top-three finish.
But they failed to wrap up top spot and automatic progression to the showpiece game after Lightning, who have also qualified for Finals Day, coasted to their target of 125 in 12.3 overs to leapfrog Storm at the summit thanks chiefly to Rachael Haynes (66no from 40 balls).
Haynes and Sophie Devine (38 off 30) made light work of the run chase after spinner Kirstie Gordon (3-19) had limited the 2017 winners to 124-6 from their 20 overs in Birmingham.
Loughborough will now rubber-stamp top spot with victory at Yorkshire Diamonds on Saturday - although Storm, three points behind Lightning, will capitalise on any slip-up if they beat Surrey Stars, live on Sky Sports Cricket.
Stars and Lancashire Thunder are battling it out for the third place at Finals Day, with Surrey three points ahead of Thunder heading into the last round of league fixtures, during which Lancashire will visit Southern Vipers.
Watch Stars v Storm, at The Oval, live on Sky Sports Cricket (channel 404) from 6.45pm on Saturday.