The top five will jockey for position during the final few weeks of the campaign and the Phoenix could conceivably win the Premier's Plate as top dog but they could easily scrape in to the finals in fifth, which would force them to go on the road in the playoffs.
After playing Perth, they travel to Brisbane to meet the Roar where the Phoenix seem unable to win, while their following match against Sydney FC in Wellington on March 29 will be tough as the game falls in a Fifa window. A collection of Phoenix players will be on international duty, which poses a problem for Merrick. Wellington will round out the season with games against the Victory, Melbourne City, Central Coast and Sydney FC.
Phoenix coach Ernie Merrick welcomed the chance to meet Perth tonight, which could help Wellington get a jump on one of the league's best sides.
"It's good for us. They're a tough team to break down," Merrick said. "They defend in their own half using a four-one-four-one type formation most of the time and then they counterattack very quickly."
Striker Andy Keogh, who has scored 10 goals in his maiden A-League campaign, is Perth's leading threat in attack; the Irishman has scored twice against Wellington this season. Perth have beaten the Phoenix 2-1 in both previous encounters this summer.
Phoenix stretch run
Round 21: Away v Perth, tonight
Round 22: Away v Brisbane Roar; Sunday, March 22
Round 23: Home v Sydney FC; Sunday, March 29 (Fifa window)
Round 24: Home v Melbourne Victory; Sunday, April 5
Round 25: Away v Melbourne City; Sunday, April 12
Round 26: Home v Central Coast Mariners; Friday, April 17
Round 27: Home v Sydney FC; Sunday, April 26