With the required run rate well over ten an over, Patel mustered just 38 from 39 balls, wasting the strike when Devon Conway and Luke Woodcock were waiting in the wings.
When finally given a chance, Conway and Woodcock added 50 from 25 balls, but it was too late, and Wellington were eliminated from playoff contention.
That left just Canterbury, who looked set to clinch their spot after making a well-balanced 190-5, and having Northern Districts in serious strife at 55-4.
ND continued to battle, and looked a long-shot when requiring 76 from 35 balls. However, Dean Brownlie smashed four sixes in five balls, and when he fell for a superb 86 from 50 deliveries, Nick Kelly (27 from 13) and import Chris Jordan (22 from 10) blasted them home for an unlikely victory.
Their comeback knocked out Canterbury, and clinched top spot on the ladder. As a result, ND progress automatically through to Saturday's final, where they will play the winner of the elimination final between CD and Auckland.
Auckland finished in second on the ladder despite losing to Otago in their final round robin clash.
Remarkably, Auckland nearly managed to defend 140 on the small Eden Park Outer Oval confines, with Otago chasing it down with one ball and two wickets to spare.
Auckland recovered from 16-4, after inexperienced Otago seamers Matt Bacon (4-31) and Jack Hunter (3-35) did the early damage, but their 139-9 should never have been competitive.
However, Otago's batsmen have struggled all season, and they too battled to begin, sitting at 9-3. Eventually, Derek De Boorder's unbeaten 50 from 40 balls got them back on track, but they still needed 10 off the last over.
There, they managed to snare just their second win of the campaign, with a Ben Lister no-ball and a Michael Rae top-edge for four the pivotal final moments.
More runs should be in store in Auckland's next clash at Eden Park, with the elimination final held there on Wednesday afternoon.
