South Australia were made to pay dearly for a series of diabolical fielding blunders as Western Australia posted a record-equalling 7-387 in the one-day cup final at the WACA Ground.
Opener Josh Inglis was dropped three times before posting 138 off 110 balls, while Cameron Bancroft (90 off 112) and Mitch Marsh (56 off 30) contributed important knocks to put WA in the box seat of Wednesday's match.
The team total equalled WA's previous best of 387 set against Queensland in 2018.
It was also the equal seventh highest in Australian domestic one-day cup cricket.
The Redbacks only had themselves to blame for allowing WA reach such a big total.
Inglis was a sluggish 26 off 42 balls with the scoreboard reading 1-55 in the 14th over when he was dropped by Henry Hunt at deep mid-wicket.
The moment proved decisive, with Inglis needing just 45 more balls to race from 26 to his maiden one-day Cup century.
Inglis was dropped again on 118 when Redbacks captain Jake Lehmann grassed him at mid-off.
The 28-year-old blaster was given another reprieve on 123 when he gloved paceman Spencer Johnson through to the keeper - only for the umpire to give it not out.
Bancroft was on 51 when Henry Thornton dropped an absolute sitter at mid-off, with the ball going straight through his hands and to the boundary.
The 227-run stand between Inglis and Bancroft catapulted WA into the box seat, with South Australia now needing to pull off a Herculean effort with the bat to secure victory.
The Redbacks' misfortune began even before play started with opener Jake Carder a late scratching after injuring his hamstring in the warm-up.
Kelvin Smith was brought in as his replacement.
WA's side was so stacked with starpower there was no room for D'Arcy Short, who had posted scores of 74 and 49 in his two recent innings.
Out of WA's XI, only paceman Matt Kelly and allrounder Aaron Hardie don't boast international experience.
Warriors paceman Jhye Richardson couldn't be considered after suffering another tear to his left hamstring last week, with the injury also ruling him out of the upcoming ODI series in India.
WA Cricket won the treble last year - the BBL title, the one-day Cup crown and the Sheffield Shield.
They have the chance to repeat the dose this summer, having already taken out the BBL crown and securing berths in the one-day and Shield finals.
South Australia are appearing in their first decider since the 2017-18 one-day final, which they lost to WA.
Their nerves were on display as evidenced by the series of easy dropped catches they would normally swallow.
Inglis cracked 14 fours and five sixes on the way to the highest score in a one-day cup final, beating the 135no from Michael Bevan in 2001 when NSW beat WA.
Nathan McAndrew copped the biggest punishment, finishing with figures of 0-99 off nine overs.
