The Sky Blues must win their two remaining matches and rely on Central Coast Mariners not to claim a point from their final outing, in order to scrape inside the top four.

Sydney face the Roar in Brisbane followed by Newcastle Jets in Round 21 while the Mariners meet Adelaide United in the final round of the season.

With a host of players still unavailable through injury, National Youth League trio Kofi Danning, Rhyan Grant and Zach Cairncross, have all been rewarded for strong efforts against the Phoenix and will once again play key roles with the season on the line.

Despite their precarious position, Kosmina says the mood in the camp remains upbeat following last week's win over Wellington.

"It makes a difference a win. It makes a big difference, so they've been a little bit more buoyant and there's a glimmer of light at the end of the tunnel," Kosmina said.

But it won't be an easy task for the men from the Harbour City who enter the clash without defender Shannon Cole's (hip) who will be replaced at right back by either Robbie Middleby or Matthew Jurman.

Marquee striker John Aloisi (quadriceps) will also remain in Sydney despite returning to full training this week.

"Johnny had a full session with the team yesterday, the first in three weeks, but he's not going to travel with the team - he's undertrained," Kosmina said.

"I spoke to Johnny about that, he's had three running sessions in three weeks and it's just not enough leg work."

Veterans Simon Colosimo and Steve Corica will also start on the bench.

Of his decision not to include Corica in the starting line-up, Kosmina admitted his reluctance to tamper with his midfield against a hard-running Roar line-up.

"As it stands at the moment we're not going to change the midfield, I think Terry McFlynn's inclusion last week made a difference."

"I think the combination of (Mitch) Nichols, (Matt) McKay and (Massimo) Murdocca is probably the most mobile and creative midfield in the competition."

"So we've got to look at who can match up with them and to be honest no one can match 'Matty' or 'Mass' in a game in terms of their running throughout a game.