The Stingrays unseated Macarthur as premiers earlier this year and were first into Sunday's decider at Balls Paddock after winning the major semi-final, but Wallin was quick to hang the favourites' tag on the Campbelltown club.

Macarthur's edge in big match experience - they won the past two deciders - made them favourites, Wallin said.

"I think we are the underdogs going into the grand final because they have been here before," he said.

"In grand finals you have to forget about the season and that bit of experience gives them an edge."

However, Wallin said the 3-2, extra-time win in the major semi-final proved Illawarra could dominate big games after a pair of slender 1-0 victories over Macarthur in the league that cancelled out a 4-0 hiding.

"I think that flattered them (Macarthur), we dominated them for 90 per cent of the game and hopefully the girls can take some confidence from that," he said.

"It's our game to win or lose, but I've seen plenty of teams dominate a season then lose a grand final."

Wallin admitted winning the league and the grand final in the season the club was promoted to the top flight would be a huge achievement.

"The league is for the coach, the grand final is for the players," he said.

Macarthur qualified for the decider after a 2-0 win over Manly at Lynwood Park last Sunday.

Although striker Michelle Heyman and midfielders Michelle Carney, Trudy Camilleri and Ash Connor are among the Stingrays' biggest names, Wallin believed his side's depth would be the key.

"We don't rely on one player, that's been a strength all year," he said.

Meantime, Illawarra will play Manly in the reserve grade decider after thrashing Sydney University 4-0 on Sunday.