Otago No 3 Gary Creedy turned 3 up on Bob Shirley but injured his back on the 12th tee block. He laboured on but lost the last three holes to finish 1 down.
This reversal gave Northland a 3 to 2 win after the result seemed set to go Otago's way with Creedy in good form.
It left Otago with one win, one draw and two losses after the fifth round. Northland has also had a bye but has now won four from four.
Northland shares the tournament lead with Auckland which also has four wins from four outings.
But in the morning Simon Boland, at No 1, met former Northland teenage star Saali Herewini, who has not lost any of his touch.
Boland had putting woes while Herewini made birdies at three, six, nine, 10, 12 and 13 to finish the game with four holes to spare.
Stephen Hitchcox turned 3 up and parred the back nine to post a win over Peter Bone on the 17th green.
Jeremy Morgan accounted for Northland No 4 after playing a match-winning shot from the 16th bunker to make a par and go dormie two ahead.
But at No 5, Kyle Geary had no answer to a barrage of birdies and lost on the 13th green.
Northland's Iain Power birdied two, three, four, six, 10, 11 and 12.
This morning Otago will be tested by the defending champion, Bay of Plenty, while the team meets Taranaki in the seventh round this afternoon.
A decision whether Creedy will compete today will be made this morning.
Should he be forced to withdraw, reserve-manager Greg Johnson will play at No 5 while Morgan and Geary will each play one position higher.
