Just before halftime is always a good time to score and the United players trotted off with heads held high, after defending stoutly in that first half when Wanderers created many chances.
A top match by goalkeeper Tom Batty and committed defence blunted the young Wanderers side and, as the half progressed, it was Southern United which looked more dangerous.
Nevertheless, there was a serious halftime team talk from coach Luiz Uehara, urging his team to continue to play controlled football, yet with a mind on Wanderers' resilient form this season in snatching late goals.
From his advanced midfield role, Ridden continued to threaten, and Henrique Viana became more involved as the game progressed.
Wanderers Andre De Jong, son of former New Zealand striker Fred, made forays into the United box, and on the left wing Nick Sugden found space to deliver crosses.
But keeper Batty's form snuffed out several free kicks and corners by Wanderers and, in the 51st minute, the industrious Peter Rae wriggled free and delivered a perfect cross for Viana to head United into a 2-0 lead.
Any thought of coasting was dispelled, however, when referee Matt Conger first punished Viana with a yellow card, then flashed a second yellow at Cam Attwood and United was down to 10 men with more than 20 minutes to go.
Coach Uehara made changes as he dragged Viana, and brought on Taylor McCormack, but Wanderers seized the moment to narrow the score almost immediately when Michael Den Heijer showed tight skill to swivel and shoot his team back in the game.
Back to 2-1 after 68 minutes and with an extra man, Wanderers pushed forward as, in a bid to tighten things up, Sam Mepham replaced Rae.
Open play produced chances for both sides as Nick Hindson burst through in a one on one with keeper Zac Speedy, then it was Batty's turn as he saved from Scott Doney.
Referee Conger played four long minutes of extra time to frazzle the nerves of coaches Uehara and Darren Hart, but it was Mepham who drew down the final curtain with a blazing shot as fulltime was eventually whistled.
''This was another step along the way,'' Uehara sad.
''We have played better and lost, but as the game went on, our players showed fitness, skill and courage against a very good young side.
''Best of all was the high level of concentration we maintained, and if we continue to achieve that ... we will pick up more points.''
