As he did with a fifth-minute goal against Wellington several weeks back, Henriques Viana cheekily chipped Waitakere keeper Danny Robinson to put Southern ahead 1-nil after just three minutes.
Brazilian football is all about clever technique and Viana now has an Otago cult following due to his mastery of making the ball do what he wants.
Inspired by the Brazilian, Peter Rae also showed his skills with a header that shaved the post, then a fierce drive that stretched keeper Robinson.
Then it was gloves off as some big tackles were made by both sides and Southern keeper Tom Batty had to make a couple of saves, the best a sizzling shot from Jack Hobson-McVeigh.
Southern retaliated when Nick Hindson curled a free kick that skiffed over Waitakere's crossbar in the 19th minute.
With halftime approaching, Southern's striker Rae boosted morale as he darted into a goal-mouth melee and drilled coach Luiz Uehara's team back into a 2-1 lead at the break.
However, Viana - who was clattered just before halftime - had to be replaced and the spring-heeled Taylor McCormack went on, as Southern attacked and forced a spectacular double save from Waitakere keeper Robinson.
Referee Conger sent a shudder through Southern ranks when he flashed a 65th-minute second yellow card at midfielder Day and United was down to 10 men.
Instead of buckling, Southern's 10 men roared into attack, and Logan Wright-Webb shocked Waitakere fans by shooting his side into a devastating 3-1 lead with 20 minutes to go.
Coach Uehara admitted it was a long 20 minutes as both Richie Cardozo and Jordan Lowden shot at goal, but Southern finished in style as Hindson went close with a final strong effort.
Considering Southern went north with a scratch team due to injuries, and reserve keeper Jefferson Potrich almost played centre half, it was a victory of some skill and great spirit to beat the ASB Premiership leader.
''The players we had seized their opportunity and showed what can be done away from home, even against a top side,'' Uehara said.
Southern United 3
Waitakere 1
