McStay was subbed out of the six-point victory during the second term with a finger tendon injury, with the Magpies recruit needing further assessment in the coming days before a call on his selection status is made.
Initial signs suggest the Pies' free agency pickup will at least miss the highly-anticipated Bombers matchup, but senior coach Craig McRae has his fingers crossed that the club "might get lucky".
"It looks like he's done a tendon in a finger," McRae said after the win.
"We'll get that scanned and assessed by an expert and then find out what that looks like. It could be operational, most of them tend to be, but we might get lucky."
Murphy has been ruled out of the Anzac Day clash after entering the AFL's concussion protocols following an off-the-ball incident with Saints forward Anthony Caminiti that left the Magpies defender groggy on the Adelaide Oval turf.
Murphy was animated toward the St Kilda bench as he made his way off the field, with McRae confirming post-game that the club will need to look into their options for Round 6.
"Murph got concussed, so he'll be out next week," McRae revealed. "The doctors have ruled that already.
"I haven't seen the incident, but he has obviously been concussed somehow. We'll get to work on what that looks like; it's not up to us to decide that, but he'll be out next week.
Nathan Murphy went down after this incident with Caminiti. Anything in it?
— Fox Footy (@FOXFOOTY) April 16, 2023
"I was on the bench when he came off. I'm not sure what was said. Don't know if Murph was concussed and didn't know what he was saying, I've got no idea.
"The reality is he came off and he said something. He was obviously upset about something."
Collingwood are likely to regain Jordan De Goey for their bout with the Bombers after the star midfielder was a late withdrawal from the match due to gastro.
Fringe tall Nathan Kreuger made his return to action on Sunday in the VFL against Box Hill as a pinch-hit ruckman, however amassed just the three disposals in a 59-point loss to the Hawks.
Stengle was subbed out of the 47-point victory and rushed to a local Adelaide hospital for an X-ray after landing on his left arm in a tackle from Eagles defender Josh Rotham.
The Cats are expected to be without the former Tiger and Crow for some time as they look to continue their run of successive wins, with upcoming matches against Sydney, Essendon, Adelaide and Richmond proving to be vital across their next month.
Chris Scott's forward line has returned to premiership form in recent weeks, with veteran Tom Hawkins and small forward Brad Close joining superstar Jeremy Cameron in booting four goals against the Eagles.
The Cats will play their first game at GMHBA Stadium for the season this week when they host Sydney on Saturday night.