Tasmania 55 for 3 beat Western Australia 53 (Webster 6-17, Stanlake 3-12) by seven wickets
Western Australia lost an incredible 8 for 1 - with their one run coming from a wide - in a batting collapse for the ages that has left their One-Day Cup defence in tatters.
They were bowled out for 53 in 20.1 overs at the WACA Ground on Friday against a rampant Tasmania attack led superbly by
Beau Webster (6-17 off six overs).
Tasmania chased down the paltry victory target in just 8.3 overs to secure a seven-wicket victory and a vital bonus point.
WA's bid for a fourth consecutive title now hangs by a thread. At one-and-three, WA need to beat Victoria, South Australia and Queensland in their remaining three games - and rely on other results to fall their way - in order to secure a top-two spot and a berth in the March 1 final.
WA were crawling at 52 for 2 in the 16th over before suffering one of the worst batting collapses witnessed in professional cricket. In the space of 28 legal deliveries, WA lost eight wickets and registered just one run - in the sundries column - as Webster and
Billy Stanlake ran rampant.
It meant WA went from 52 for 2 to all out for 53, with not a single run scored by the players batting at No. 5, 6, 7, 8, 9, 10 and 11.
The out-of-form Cameron Bancroft was the first to fall in the collapse when trapped lbw by Webster. Ashton Turner also fell lbw to Webster three balls later, and Josh Inglis was bowled by a Stanlake pearler one ball after that.
Cooper Connolly, Hilton Cartwright, Ashton Agar, Jhye Richardson and Joel Paris all posted ducks as WA's innings was brought to a crashing end.
Opener D'Arcy Short top scored with 22 in a sorry looking scoreboard for the three-time defending champions. WA fell short of their previous lowest score, the 59 they posted against Victoria at the MCG in 1969.
Webster was the hero for Tasmania, claiming the early scalp of Short before kick-starting the collapse in a career-best display. Stanlake was also hugely effective, with his removal of Inglis among the highlights of the innings.
In reply to WA's embarrassing total, Tasmania raced to 27 without loss after three overs as opener Mitchell Owen let loose with a series of powerful heaves.
Tasmania lost 3 for 1 as Caleb Jewell, Jordan Silk and Owen fell in quick succession, but Matthew Wade guided them home.
The result marked Tasmania's first win of the season, after a loss and a no-result from their first two games.