After eight players were missing through injury and personal commitments against Hawkes Bay last weekend, the list of unavailable players is down to just four this week.
Midfielder Stu Kelly (ankle), defenders Craig Ferguson (knee) and Ross Howard (groin), and forward Josh Stewart (calf) will all miss the match through injury.
Howard is at least a few weeks away from returning, while Ferguson is set to have an MRI scan on his knee next week.
Stewart got through training on Thursday but coach Mike Fridge does not think he is ready to play.
Kelly's ankle injury is not thought to be as serious as first expected, but he will miss at least one or two games.
However, captain Matt Joy, midfielder Tim McClennan and defender Tristan Prattley are back.
Regan Coldicott and Morgan Day were also available after missing last week but were not selected.
''I had a little bit more selection problems this week than last week,'' Fridge said.
''Last week, it was easier because if you were fit you could well be in the squad. This week, I had more people to choose from. The more players we have fit and challenging for places, the better.''
With two losses and no goals scored in its first two games, Southern United will attempt to kick-start its campaign against winless Phoenix.
The Wellington-based team has a 3-0 loss to Canterbury United and a 3-1 loss to Auckland City to show from its first two games.
Fridge said it was important his team did not panic after its lacklustre start to the competition, but admitted tomorrow's game was big.
''I want to try and go at this game right from the start,'' he said.
''I don't want to just ease into it. We've been drumming into the players that once the whistle goes, let's just try and take the game to them. Let's force them on to the back foot and let's have a go at them.''
Southern United trained three times during the week and talked about taking more shots at goal in the attacking third. Fridge was frustrated by the side's unwillingness to pull the trigger in a toothless 3-0 loss to Hawkes Bay last weekend.
''We trained an extra night this week,'' Fridge said.
''The boys were keen to do that to keep things ticking over. The atmosphere has been good. I just want to keep everything focused and upbeat.''
Without revealing too much, Fridge hinted that he could tinker with the formation tomorrow in a quest to find the back of the net.
Two former Dunedin footballers - James McGarry and Joel Stevens - will front up for the Phoenix tomorrow.
Stevens, a former Green Island striker, scored a hat trick to help sink Southern United 4-3 in Invercargill last season.
McGarry, one of the best New Zealand players at the recent under-17 World Cup in Chile, is the only Phoenix player to score so far this season.
''They are two good players,'' Fridge said.
''They will be dangerous and I'm sure if we give them chances they will cause us problems. I wish them well in their careers, but I don't wish them well [tomorrow] because I want us to win the game.''
The match kicks off an important four-game stretch before Christmas for Southern United, with three of those matches at home - two at Forsyth Barr Stadium and one at Rugby Park in Invercargill.
Waikato-Bay of Plenty looms at Forsyth Barr Stadium next weekend, before the team is on the road against Wellington in a fortnight.
Its last match before the break is against Canterbury United in Invercargill on December 20.
Southern United v Wellington Phoenix
Forsyth Barr Stadium, tomorrow, 2pm
Southern United: Tom Batty, Jude Fitzpatrick, Matt Joy (captain), Rhys Ruka, Seamus Ryder, Andrew Ridden, Sam French, Andrew Mobberley, Tim McLennan, Zane Green, Tom Connor, Harley Rodeka, Tristan Prattley, Tom McBride, Michael Hogan, Sam Redwood
Wellington Phoenix (probable): Troy Danaskos, Dylan Fox, James McGarry, Tamupiwa Dimairo, Joel Stevens, Oliver Sail, Luke Tongue, Sarpreet Singh, Ruairi Cahill-Fleury, Liam Wood, Joe Bell, Cherbel Khouchaba, Louis Evans, Max Mata, Washington Bgoni.
