The Volts would need to beat Canterbury in Timaru today by plenty, pick up a bonus point and lift their net run rate.
If Otago loses, it could drop as low as fourth place and face a sudden-death play-off match against either Northern Districts or Auckland.
Either way, Otago is through to play-offs and will be desperate to avoid a repeat result of last year's fixture at Aorangi Park.
Canterbury posted the highest one-day tally scored in New Zealand - 410 for five.
Otago made a valiant chase, reaching 371 for seven - its highest one-day total.
Canterbury all-rounder Rob Nicol's punishing innings of 132 from 108 deliveries set up the massive total, and some lusty hitting from Peter Fulton (88 off 61) and Shanan Stewart (55 off 21) completed the rout.
Nicol has been in great form again this season.
He is the competition's leading scorer with 437 runs at an average of 72.83.
The 27-year-old opener has been remarkably consistent with scores of 42, 58, 81, 84, 67 and 105.
He has also been more than useful at the bowling crease with nine wickets at 25.44 and an impressive economy rate of 4.43.
With form like that it is very surprising Nicol missed out on a place in the World Cup squad.
But while his skills seemed to have escaped the national selectors, Otago coach Mike Hesson said he was a player the Volts were hoping finally has a long overdue off day.
"He's a player that has performed well against us," Hesson said.
"We've seen quite a lot of Rob and he is a very consistent performer for them.
"With him, [Michael] Papps and [Peter] Fulton, their top order has gone well and they rely a lot on those guys.
"If we are able to make early inroads into that order then we are going to test the strength of their middle order."
Canterbury thrashed Otago by 99 runs at the Queenstown Events Centre last month with Nicol (58), Papps (63) and Fulton (87) setting up a total of just under 300 runs.
Otago goes into the game with form batsman Neil Broom under the injury cloud.
The right-hander has scored back-to-back 100s but sustained a nasty blow on the toe of his left foot in the seven-wicket loss to Auckland on Sunday.
Shaun Haig has been brought into the squad as cover but Hesson is hopeful Otago's leading scorer will play.
"It was a pretty nasty blow on his toe and hindered him later on in his innings.
"But he is in superb form and is obviously really keen to play.
"If he is fit we're really keen to have him."
In other changes, Black Caps offspinner Nathan McCullum returns to national duty and all-rounder Ian Butler has a "couple of niggles" and is being rested.
Pace bowler James McMillan and left arm seamer Craig Smith replace McCullum and Butler.
Otago v Canterbury Aorangi Oval, today
Otago: Aaron Redmond, Michael Bracewell, Neil Broom, Craig Cumming (captain), Darren Stevens, Darren Broom, Derek de Boorder, Neil Wagner, Nick Beard, James McMillan, Craig Smith, Warren McSkimming, Shaun Haig.
Canterbury: Rob Nicol, Michael Papps, Peter Fulton (captain), Dean Brownlie, Shanan Stewart, Reece Young, Andrew Ellis, Todd Astle, Carl Frauenstein, Martin Kain, Mitchell Claydon, Ryan McCone.
