Victoria produced an astonishing batting performance to post their greatest pursuit in one-day cricket and beat Tasmania by four wickets at the MCG on Saturday night.

The Vics looked headed for an early night chasing Tasmania's 7-300 when their first four batsmen were out before the halfway mark of the innings.

But Aaron Finch made a career-best 87 not out from as many balls and paceman John Hastings walloped 41 not out from 28 deliveries to take the Bushrangers (6-301) to victory with four balls remaining.

Victoria's amazing comeback was completed when Finch slugged Brett Geeves down the ground for six on the second ball of the final over.

Victoria eventually took 85 runs from the 40-over mark for just the loss of Matthew Wade (30), whose partnership of 75 with Finch gave the home side a shot after they slumped to 5-149 in the 30th over.

Finch and Hastings finished with an unbroken stand of 77 from 51 balls.

While Finch was the one fist pumping at the end, the match was also memorable for a breakthrough by Tasmanian opener Rhett Lockyear, who made 111 after getting a late call-up to replace injured allrounder Luke Butterworth.

Lockyear came into the match never having bettered 20 in his previous five one-dayers but batted so freely he reached three figures in the 30th over and a massive score beckoned.

He was out slogging, but captain George Bailey (63) and Travis Birt (66 from 54 balls) made sure Lockyear's start was not wasted by taking to all of the Bushrangers' bowlers.

Victoria's problems in the field were compounded by having only four specialist bowlers because they have a string of players either injured or with the Australian squad in India.

Victoria's chase looked in grave doubt when Chris Rogers was out to a shocking decision, ruled caught behind when the ball clearly came off his pad, and star Brad Hodge (42) was out in the 25th over.

Finch, 22, began slowly during the rebuilding stage, but showed his power late in the game with three sixes.

Victoria are now second on the table, behind Queensland, with two wins from two games, while the Tigers have one win and two losses from their three matches.

The game was marred by a hold-up early in Victoria's innings when a fan walked on to the ground and then broke free from the hold of security staff.

Finch admitted he relished the extra responsibility once Hodge departed and said he and Wade felt the momentum shift once their partnership reached 50.

"Any time you can contribute personally to a win is a fantastic thing," he said.

"There's one thing about being part of a winning team and another thing being a contributor in a winning team.

"It's a bit of a weight of my shoulders that I've contributed to one.

"Coming in to today my highest score was 33 and after seven games batting at six that's probably not good enough, and I'm thankful the selectors stuck with me for a while and I've repaid them today."

Lockyear was pleased to grab his opportunity, but admitted the Tigers had let slip from a position of control.

"Probably but I think if you get two blokes who are hitting the ball that cleanly there's not much you can really do," he said.

"It's a bit unfortunate but they were batting so well."

Before Saturday Victoria's biggest successful pursuit was the 2-296 they amassed to beat NSW in Canberra three seasons ago.