Joe O'Donoghue opened the scoring early for the deposed champions, but Matt Nixon levelled the scores inside the first quarter hour and the match entered half time all square.
After the break, Unicol blew the Lakesiders away thanks to goals from Krishaant Singh, Thomas Wright, Shaun Morgan and an own goal in a result that now gives Unicol a sniff of a top three finish.
Ōtūmoetai now look like they will finish as runners-up after beating West Hamilton United 3-1.
An own goal, alongside strikes from Jordi Langton and Scott Walpole, were enough to increase Ōtūmoetai's lead over Taupō to four points. They still have a game to play - against Matamata in a fortnight - while Ōtūmoetai have two visits to Hamilton, to play Melville United and West Hamilton United, over the next two weeks.
West Hamilton must now win their final two matches, first against Unicol then Ōtūmoetai, to claim the six points they need to jump ahead of 10th placed Te Awamutu.
In other premiership matches at the weekend, Tauranga Boys' College completed Safer Team Te Puke United's tough season at the top, wrapping up a 2-0 victory over the league's bottom side; Ngaruawahia United beat Tauranga Blue Rovers 3-1 and Matamata Swifts drew 2-all with visiting Melville United.
The Soccer Shop WaiBop Football results:
Premiership:
Waikato Unicol 5-2 Taupō, Tauranga Boys' College 2-0 Te Puke United, Ōtūmoetai 3-1 West Hamilton United, Ngaruawahia United 3-1 Tauranga Blue Rovers, Pāpāmoa 4-0 Te Awamutu, Matamata Swifts 2-2 Melville United.
Championship:
Waikato Unicol Reserves 1-3 Taupō Reserves, Ōtūmoetai Reserves 1-5 Claudelands Rovers, Hamilton Wanderers 9-0 Tauranga Blue Rovers Reserves, Flying Mullet Pāpāmoa Reserves 1-2 Tauranga City, Matamata Reserves 0-11 Otorohanga, Tokoroa 2-1 Cambridge.
W-League:
Tauranga City 2-3 Claudelands Rovers, Ōtūmoetai 1-1 Melville United, Tilemax Pāpāmoa 0-1 Whakatāne Town.