Multiple heroes emerged for the Volts.
Captain Jacob Duffy claimed a career-best six for 35.
Veteran top-order batsman Brad Wilson posted his maiden one-day century and nearly carried his bat.
Michael Rippon swatted the first two deliveries of the final over for four to help relieve the pressure before getting out with victory in sight.
It was quite a game.Canterbury reached 270 thanks to a marvellous 104 from Chad Bowes.Canterbury skipper Cole McConchie played a valuable support role with 42, and Cameron Fletcher blasted 47 not out from 37 deliveries.
He also helped smash 20 off the final over of Canterbury’s innings which almost proved the visiting side’s undoing.
"We’ve got ourselves into that playoff and that is a huge step forward for this team," Volts coach Rob Walter said.
Otago has had two lean years in all three formats. That fact coupled with four high-profile departures left many supporters with low expectations.
But Otago has defied it critics and is finding ways to win games it was losing last season.
"Obviously, I’m incredibly proud of the fight the boys showed again.
"Batting certainly got tougher when the balls got softer but we stuck in it.
"They are positive signs that we’ve now won two really close games — one with the ball and one with the bat."
Duffy snaffled his second five-wicket bag this season and third in the format.
The 24-year-old struck early, removing opener Jack Boyle before he could get going.
But Canterbury rallied. Bowes and McConchie put on 78 for the third wicket and got the home side into a very solid position.
Duffy brought himself back on and helped turn the match when he captured the wickets of Leo Carter (10) and Jeff Case (4).
But the big breakthrough came at the other end when Bowes top-edged a sweep shot off the bowling of Rippon.
Bowes had not long brought up his fourth one-day century and left with his side well-placed. But Duffy ran through the tail, picking up three more quick wickets.
Wilson anchored the chase with a superbly paced 126. He was overlooked at the start of the campaign. But with Hamish Rutherford unavailable and Shawn Hicks out of form, Wilson was brought it.
He made a golden duck in his last innings but responded with a match-winning innings.
"We needed someone to step in and what better way to do it than with a hundred in his second knock [this season].
"He has come in at a crucial time in the tournament and delivered for us."
In Lincoln, Auckland beat Northern Districts by 58 runs by the Duckworth-Lewis-Stern method. Colin Munro smashed 143 to help the Aces secure an important bonus point.
The Aces (21 points) are in third and enjoy a five-point buffer over the fourth-placed Northern Districts (16 points) with one round remaining.
Northern will need a bonus-point win against Wellington and for Auckland to lose its last round-robin game, which is against Otago, to have a chance of sneaking into the playoffs.
Wellington leads the competition with 27 points but suffered a setback. It was beaten by Central Districts by seven runs by the Duckworth-Lewis-Stern method.
Wellington appeared the have the chase in hand when the rain set in at Lincoln. But it was behind the par score at the time.
• Otago opener Hamish Rutherford continues to impress this season. The 29-year-old left-hander scored a century for New Zealand A in its four-day match with India A at Mt Maunganui.
He struck 17 fours and a six in his innings of 114. It was Rutherford’s fourth hundred in all formats this season.
New Zealand A declared at 458 for nine in reply to
India A’s 467 for eight declared. At stumps on day three, India was 35 for none and leads by 44 runs.
