Graham Arnold's Sky Blues sit behind Victory, who are three points clear at the top, ahead of a trip to Wellington.
The Phoenix are a point behind Sydney, who will seal a top-two spot and a home semi-final should they avoid defeat.
Arnold's side are unbeaten in 13 away games this campaign, and they have won back-to-back games ahead of their trip to Westpac Stadium.
Sydney could still finish top, but they will need a win and goal difference turnaround of seven.
That is unlikely, given Victory host the eighth-placed Central Coast Mariners at AAMI Park on Sunday.
Austria captain Marc Janko is on track to win the golden boot, having scored 16 goals for Sydney – three more than Phoenix attacker Nathan Burns.
Wellington have been in scratchy form, with Ernie Merrick's side coming from behind to edge the Mariners 3-2 last time out.
Perth Glory, who visit the second-bottom Western Sydney Wanderers on Saturday, currently sit third but will be sent down to seventh for salary cap breaches.
Adelaide United are still eyeing third spot ahead of a meeting with Melbourne City at Coopers Stadium on Saturday.
If Josep Gombau's men win and the Phoenix lose, the Reds will jump into third and host the Brisbane Roar in the first week of the finals.
The Roar, fresh from a 1-0 win at Beijing Guoan in the AFC Champions League in mid-week, host the bottom-placed Newcastle Jets on Friday.
Victory complete the round when they host the Mariners, and Kevin Muscat's men are set to win their first piece of silverware since 2009.
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