A below-strength Waikato side needed a late try to edge past Counties Manukau 32-28 in Pukekohe on Saturday.
A 76th minute try from lock Anthony Wise saw the new Ranfurly Shield holders come from behind to claim the spoils in a thrilling clash in perfect conditions for running rugby.
Three days ahead of their Log o' Wood defence against Hawke's Bay, the Mooloos rested more than 10 of their Shield-winning squad and trailed 25-10 with 15 minutes to play.
But visitors bounced back with three late tries to snatch their third win in a row, and in the process secure a place in the ITM Cup Premiership next year.
Counties Manukau are already guaranteed of making the semi-finals in the second division Championship with two games to play.
Both sides scored four tries, but superior kicking from Waikato full-back Trent Renata proved the difference.
The game looked down and dusted when outstanding Steelers centre Bundee Aki showed electric speed to cross for his second try in the 58th minute and give the host a 15-point lead.
But, two tries from Waikato centre Save Tokula pulled them to within three points before Wise crashed at the death to complete a classic comeback.
For Counties Manukau:
Tries: Aki 2, Nanai-Williams, Stowers
Pens: Nanai-Williams, Laulala
Tries: Tokula 2, Webber, Wise
Cons: Renata 3
Pens: Renata 2
Counties Manukau: 15 Tim Nanai-Williams, 14 Tony Pulu, 13 Rey Lee-Lo, 12 Bundee Aki, 11 Sherwin Stowers, 10 Baden Kerr, 9 August Pulu; 8 Adam Cathcart, 7 DJ Forbes (c), 6 Jimmy Tupou, 5 Daniel Adongo, 4 Ronald Raaymakers, 3 Matt Talaese, 2 Mahonri Schwalger, 1 Simon Lemalu.
Replacements: 16 Suliasi Taufalele, 17 Maka Tatafu, 18 Maama Vaipulu, 19 Mark Selwyn, 20 David Bason, 21 Ray Laulala, 22 Tyrone Lefau.
Waikato: 15 Trent Renata, 14 Declan O'Donnell, 13 Save Tokula, 12 Joe Perawiti, 11 Joe Webber, 10 Piers Francis, 9 Brendon Leonard, 8 Alex Bradley (capt), 7 Jono Armstrong, 6 Rory Grice, 5 Sam Kilgour, 4 Anthony Wise, 3 Ted Tauroa, 2 Vance Elliott, 1 Latu Talakai.
Replacements: 16 Kalem Chan Boon, 17 Loni Uhila, 18 Johan Bardoul, 19 Adam Burn, 20 Ruaan Du Plooy, 21 Sam Christie, 22 Navi Sikivou.