"We're going there to get the three points," he declared after the side's final training session yesterday.
"It's tight at the moment around that part of the table and they'll be looking at it the same way we are. It's important we put our stake in the ground in that top six and we've got an opportunity to do that."
Greenacre also revealed the players have had little in the way of a break, even though they had no game last weekend due to the split nature of this A-League round.
"There's no doubt that we're going there for the win," said veteran striker Shane Smeltz.
"It's been a clear message over the last couple of weeks. We've put the work in. We've had a good heavy week and the boys are ready," he said.
The Phoenix have collected just one point from a possible six against Western Sydney this season, coming from 2-0 down to draw 2-2 at Mount Smart Stadium in December, before a comprehensive 3-1 defeat in New Plymouth last month.
"We actually owe Western Sydney a performance because our performance last time in [New Plymouth] wasn't up to standard. We didn't turn up that day but we really need to turn up this weekend," said Greenacre.
The Phoenix will be without defender Jacob Tratt, who is unavailable for personal reasons, while midfielder Michael McGlinchey - who hasn't played since February 9 - remains sidelined with a knee injury, despite being called into the All Whites squad to face Fiji in their upcoming World Cup qualifiers.
On the plus side, the Phoenix welcome back Italian defender Marco Rossi who missed the last game with a hamstring injury and will be buoyed by their last two results, a 2-1 win in Brisbane and a 3-3 draw with red-hot Perth Glory.
They've also won two of their last four away matches against the Wanderers, scoring nine goals in the process.
