Western Australia 5 for 369 (Green 114, Marsh 113, Worrall 2-62) beat South Australia 356 (Head 142, Nielsen 110, Guthrie 2-55) by 13 runs
Cameron Green and Travis Head traded spectacular centuries at the WACA but it was a South Australia collapse that decided the game as Western Australia secured the win in a contest that had 725 runs, including four centuries.
Green scored his first one-day hundred from 82 balls, powering the latter part of Western Australia's innings with some fierce strokeplay, but Head responded in kind with a brilliant 68-ball century, which put his team on course in a rollicking stand of 226 in 25 overs with Harry Nielsen, who struck a maiden one-day hundred too.
However, when Head was run-out - beaten by Green's strong arm - it started a collapse of 9 for 76 as the middle order lost its cool. Alex Carey was also run-out, through an excellent gather by wicketkeeper Josh Inglis, without facing a ball before Nielsen and Callum Ferguson brought the equation down to 55 off 43 balls with seven wickets in hand.
Ferguson missed a hack across the line against Aaron Hardie, who then had Nielsen caught at deep cover, and the lower order couldn't recover. Cam Valente gave South Australia an outside chance of getting 15 of the last over but he became the fourth run-out of the innings as he tried to keep the strike but failed.
It meant another agonising near-miss for the Redbacks on their trip west after they came within one wicket of securing victory in the Sheffield Shield.
While the game was decided by a collapse and some rather headless batting, there was some outstanding strokeplay throughout the day.
Green, who scored an unbeaten 168 in the Shield game, had taken time to lay himself a base and was 33 off 45 after playing out a maiden from Daniel Worrall in the 33rd over. He then cut loose, bringing up his half-century with three consecutive sixes off Head and there was no stopping him after that. The last 56 balls of his stay brought 111 runs as he carted the ball to all parts of his home ground, which included five fours off the first five balls of Worrall's ninth over.
Shaun Marsh had earlier brought up his 19th hundred in the format off a comparatively sedate 99 deliveries in a stand of 156 in 22 overs for the third wicket with Green. Green and Inglis then added the finished touches with a partnership of 88 in seven overs.
Remarkably, though, it did not look like it would be enough as Head produced a thrilling display of striking, which followed his double-century in the Shield earlier in the week. He struck his first ball for four although he wasn't consistently above a run-a-ball until passing 20.
He went to his fifty from 39 balls with a six off Charles Stobo in the 24th over, which cost 21 and really kick-started the chase when the required rate had passed nine an over. After celebrating the hundred, which required just a further 29 deliveries, he was sending the ball to and over the boundary almost at will until he was caught just short coming back for a second.
Western Australia had an opening and they made it count, although the Redbacks will know a stunning chase slipped from their grasp.
Andrew McGlashan is a deputy editor at ESPNcricinfo