Ben Sigmund has also been limited in training this week and Merrick said he might have to give the veteran a rest on Saturday, although that would split the strong partnership Sigmund holds with Andrew Durante in the heart of defence.
"It's not a great thing to break up Sigmund and Durante who are in form but it may need to happen," Merrick said.
Sigmund will likely be assessed during the side's final training session tomorrow.
Michael Boxall and Michael McGlinchey were also sore this week but look likely to be available for selection against Perth.
Meanwhile, Phoenix midfielder Roly Bonevacia said he expected to make a decision next week with regards to whether he would take up an offer to play for Curacao against Montserrat during the next Fifa window at the end of the month.
Bonevacia, a former Dutch youth international, qualifies for Curacao through his parents. The 160th-ranked Curacao were previously known as Netherlands Antilles before that country was dissolved in 2010.
"That's his call but it's just nice to be wanted, internationally," Merrick said on behalf of Bonevacia.
The 23-year-old Bonevacia had expressed a desire to stay in New Zealand and eventually qualify to play for the All Whites but because of his youth career with Holland he would not be able to meet the requirements to switch his allegiance.
If he was to make the journey to play for Curacao, he would also miss two A-League fixtures.