"We don't feel he's match-fit enough," Greenacre said.
"We need everybody that's fully fit raring to go, and we don't feel Mike is right at this minute."
The seventh-placed Nix head across the Tasman with their finals hopes hanging by a thread, sitting two points outside the finals.
Even a victory against the Wanderers, which would push them into sixth, may not be enough with fixtures against Melbourne Victory, Sydney and Brisbane Roar looming.
Their home match against Newcastle will also be complicated by the loss of their All Whites regulars, including McGlinchey, Andrew Durante, Glen Moss, Shane Smeltz and Tom Doyle, on international duty.
Greenacre was undaunted by the run-in, saying his side would approach the Wanderers and all subsequent games in the same manner.
The travelling Nix party was fully fit and boosted by a two-week football lay- off, in which Greenacre and Buckingham put them through a "mini pre-season".
Italian defender Marco Rossi has returned from injury, while Gui Finkler will have another two weeks under his belt after returning from parental leave in Brazil.
The Wanderers, meanwhile, have just returned from a trip to Korea, where they won their Asian Champions League clash 3-2 over FC Seoul.
"It's in our hands and that's all you can ever ask for - you don't want to be reliant on other teams, other results," Greenacre said.
"It's important we put our stake in the ground in that top six."
Striker Smeltz echoed his coach's thoughts, saying his team's approach would remain the same after their 3-3 draw with Perth Glory a fortnight ago.
Offensive combinations were firing and the side would be travelling to the Harbour City for all three points.
"There's no doubt everyone's talking about it as a six-pointer," the 35-year-old striker said.
"Nothing changes for us - we know we have the quality, and the last couple of weeks have shown the goals are flowing again."
-AAP
