However, Dylan Fox's excellent performance in replacing Rossi off the bench will help alleviate fears over the Italian's absence, while Matt Ridenton, a stand-out in midfield last weekend, will shift to right back to cover Tratt's absence.
Gui Finkler, who has just returned from time in Brazil with his wife and newborn daughter, is most likely to fill the No 10 role.
A win for the Phoenix tonight would lift them -- at least for a few hours -- into the top six. However, they face a red-hot Perth side who have climbed to third on the table following a 10-game run during which they've lost only once. Attackers Andy Keogh, Adam Taggart and Diego Castro have combined for 27 goals, two more than the entire Phoenix team this season.
Phoenix striker Shane Smeltz -- who had three seasons with Perth from 2011 to 2014 -- netted his 92nd A-League goal last Saturday and typified the side's fighting spirit by running tirelessly until the final whistle.
In his long football career, the 35-year-old All Whites marksman said he had often seen seasons swing on single results.
"There can be turning points in a season. It can all look doom and gloom and then you can go on a run," he said.
"Last week is probably a good starting point. There were a few issues off the pitch, a few meetings during the week, some serious talks between players and coaching staff and we all looked at ourselves in the mirror a little bit and then went away and had a great result.
"You could possibly look at that and say we've turned a corner a little bit, but it's up to us now to make sure we show that consistency week-in, week-out for the remainder of the season."
The Phoenix have never lost in Auckland, having won three and drawn three of their previous six A-League games in the city. This will be just their second visit to Albany, having beaten Melbourne Victory 2-0 there in December 2015 on a pitch resembling a patchwork quilt.
However, the Phoenix haven't beaten Perth on New Zealand soil in over six years.