Defender Kristian Gibson, from Northern Ireland by way of Nelson, has been signed by the club.
The 22-year-old has been playing for Nelson Suburbs in the Mainland Premier League, having arrived in the country at the beginning of the winter football season.
He joins a contingent of five Irishmen in the squad, all of whom played last year, along with the departed Eric Molloy.
However, Southern United CEO Chris Wright said the club's existing Irish connection had nothing to do with the signing.
''It's just a coincidence.
''The guys we brought over last year were from the Republic [of Ireland], so different country, although connected to each other.
''But he was just a player that looked good; [coach Paul O'Reilly] liked the look of him.
''There's no sort of connection with the existing team.''
Wright said O'Reilly had been scouting both the Southern and Mainland Premier Leagues for quality players.
It was seen as a logical place to look and it was more achievable to bring players down from there, rather than the North Island or overseas.
O'Reilly liked what he saw in Gibson and brought him down to train with the wider squad last weekend.
He impressed, and after several conversations it was decided to bring him on board.
Wright said there were several ways he could bolster the club.
''He's a centre-back, which is a position that, although we've got some local options that are good, we are a bit short on. So, primarily, our defensive structures will be improved with him in the squad.
''He is very tenacious, very brave.
''He's been coached at the highest level - he's come through the Rangers academy in Scotland, so he's good footballer.''
Despite having picked up two suspensions through red cards, Gibson has been said to be a top performer for Nelson Suburbs.
He will join the club in late September.
Wright would not confirm reports the club was also pursuing Omar Guardiola, who was playing in Nelson, saying the club was ''looking at a number of players''.
He said several players from the local premier league had been secured and he was also looking at quality from around the South Island and, potentially, ''one or two other signings''.
