The State Championship will go down to the last day of the last match of the season, courtesy of a thundering Auckland first-innings middle-order crash.

Four wickets for six runs sent the championship leaders reeling from a comfortable 129/2 to a precarious 135/6.

They never really recovered - and that set off a rush to the calculators as the net runs per wicket prospect that had hovered over this match reared its ugly head.

With the fall of the ninth wicket at 215/9, still 44 behind the follow-on mark, Auckland looked at the numbers and declared. Wellington, also looking at the mathematical options, decided to bat again rather than enforce the follow-on. They ended the day on 10 for one when bad light brought matters to an early close, 204 ahead and setting up the prospect of a fascinating day.

A morning session in which honours were even at 96/2 gave no indication of the drama pending. The opener Tim McIntosh and all-rounder Sanjeewa Silva had looked comfortable as they developed a third-wicket partnership that threatened to finally douse the slim Wellington title hopes.

However, they had not counted on the accuracy of the first change medium pacer Iain O'Brien and the left-arm spin of Luke Woodcock. In four overs in the middle of the afternoon, Woodcock sent back the big pair, Silva for 33 and McIntosh a confident looking 68, ending the partnership at 78, while O'Brien gave neither Tama Canning nor the debutant Matt Cairns time to settle.

O'Brien ended the day with three for 41 off 21 overs and Woodcock two for 33 from 15 to be the pick of the Welllington bowlers.

The Auckland captain Brooke Walker and the in-form Rob Nicol led a slow fight back until Walker's demise on the last ball before tea for 10 at 163/7. There was a flurry of action from Andre Adams (16) after tea to take it to 195/8 before his departure, O'Brien's third wicket of the day.

Nicol soldiered on with the assistance of Reece Young but a mid-pitch mix up leading to Nicol's run out for 42 really set the calculators going. At 215/9, Walker declared, balancing the number of runs his last wicket pair might produce against the effect on the average runs per wicket rate of the quick loss of the last wicket.

Wellington's calculations are unlikely to have included the early departure of Chris Nevin, caught off Gareth Shaw by Canning at the single slip Auckland had in place to supplement the four boundary riders charged with keeping the runs down.

The Auckland collapse and the various mathematical permutations have set up a last day of the competition that a final would have been hard pressed to match.

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