Otago can clinch a playoff spot with a win against Canterbury at the University Oval on Sunday.
The Volts (20 points) lead the twenty20 standings with five wins from seven games and another four points would provide a guaranteed finish in the top three.
Northern Districts is in second place with 18 points.
It plays Central Districts in New Plymouth tomorrow and a win would see it go top if Otago falls to Canterbury.
Auckland shapes as the other major threat. Canterbury dispatched the Aces by six wickets at Hagley Oval on Thursday evening but it is in third place with 14 points and with a game in hand.
Canterbury (10), Central (10) and Wellington (8) are at very long odds of reaching the playoffs.
Otago has made one change to its squad for the Canterbury game, with pace bowler Michael Rae making room for Black Caps all-rounder Jimmy Neesham.
Neesham was a late inclusion in the Otago squad for the match against Wellington at the Basin Reserve on Wednesday, but was not included in the starting XI.
He has been picked as a specialist batsmen and will probably start ahead of Josh Finnie or Sam Wells.
Both have made an impact with the ball recently. Wells took three wickets in one over to help the Volts beat Wellington by 19 runs.
Finnie was not required to bowl in that match but starred in Otago's eight-wicket win against Northern Districts at the University Oval earlier in the month.
He took four for 11, so it will be an interesting dilemma for Otago coach Nathan King.
However, Otago could use an extra batsman.
While the top four have all had their moments, the Volts middle order has looked vulnerable.
Neesham will add depth and his expected appearance in the blue and gold will be a relief.
A back complaint left him sidelined for six months this year.
He returned to the national side for the tour of Zimbabwe and South Africa in August and played in the first test against Australia in Brisbane.
But he was ruled out for the remainder of the series when the back pain returned.
Otago has two batsmen in the top 10 scorers.
Neil Broom is in third place with 234 runs at an average of 58.50, and Michael Bracewell is placed fourth with 211 at 42.20.
But it is Otago's attack which has arguably made the biggest impact.
Jacob Duffy is the tournament's leading wicket-taker with 12 wickets at 16.58.
Nathan McCullum (3rd), Wells (4th) and Warren Barnes (8th) are all in the top 10.
When it comes to economy, Otago has five of the top six.
The Volts have been brilliant at restricting their opponents and have been well led by captain McCullum, whose 10 wickets have come at the miserly economy rate of 5.37.
Otago v Canterbury
University Oval, today at 1pm
Otago: Anaru Kitchen, Neil Broom, Michael Bracewell, Brad Wilson. Jimmy Neesham, Nathan McCullum (captain), Derek de Boorder, Sam Wells, Bradley Scott, Jacob Duffy, Warren Barnes, Josh Finnie.
Canterbury (possible): Ronnie Hira, Cameron Fletcher, Henry Nicholls, Peter Fulton, Leo Carter, Andrew Ellis, Cole McConchie, Logan van Beek, Todd Astle, Edward Nuttall, Hamish Bennett, Ryan McCone.
