Muscat couldn't complete training on Wednesday after damaging his AC joint, an injury which Phoenix coach Ernie Merrick said shouldn't keep him out for more than a week.
The 30 year-old left back's position is likely to be covered by a switch for Louis Fenton, with Michael Boxall inserted at right back. However, Merrick wouldn't rule out promoting fit-again Tom Doyle.
Australia striker Nathan Burns (hip) and midfielder Alex Rodriguez (hamstring) are fit and available after missing the 2-1 win away to Perth Glory which earned Phoenix top spot in the league, while a number of backup players have shaken off niggles.
"There's a lot of life about the place, everybody wants to make themselves available, I guess," said Merrick, who confirmed midfielder Roly Bonevacia has turned down an invitation to play for the Caribbean island nation of Curacao.
Dutch-born Bonevacia, 23, played at age group and Olympic level for Netherlands but has a family link to the tiny nation ranked 160th in the world.
He had considered the offer to switch allegiances, which would have cut into his Phoenix duties over coming weeks.
"Roly's decided at the moment he's going to represent our squad and hopefully get into the finals," Merrick said.
"So he's prioritised his future."
