A potential semifinal against the Victory for the Phoenix would be at AAMI Park on Sunday, May 10. The A-League grand final will be played on the weekend of May 16-17.
In this week's other elimination final, Adelaide United, who finished third, will host the sixth-placed Brisbane Roar on Friday.
If Brisbane upset Adelaide and the Phoenix beat City, the Phoenix will play a semifinal against Sydney FC across the Tasman on Saturday, May 9.
Merrick's side had their chances to beat Sydney last night but after midfielder Roly Bonevacia missed a penalty in the early stages, their heads dropped.
"I thought it was a really good effort," Merrick. "Sydney are a good team. They've got some really good quality players.
"We just didn't have key strikers in goal-scoring positions when it counted."
Merrick made a handful of changes to his side from the playing XI that beat Central Coast 3-2 the previous week and goalkeeper Glen Miss missed last night's game with a minor knee injury.
"I thought he'd be fine but he didn't feel right for this game," Merrick said.
Backup custodian Lewis Italiano filled in and made his A-League debut and looked assured but Moss should return for the match against City.