Melbourne will investigate whether a delayed onset concussion was behind a worrying moment where unsteady defender Harrison Petty had to be helped from the ground in the Demons' win over Brisbane.
And Brisbane will have to see how backman Noah Answerth responds to his own latest concussion setback.
After turning over a kick-in to Will Ashcroft for a Brisbane goal just before three-quarter time of Melbourne's 16.8 (104) to 15.12 (102) win, Petty appeared visibly shaken and was surrounded by teammates.
Play was stopped as trainers assisted Petty from the field.
"It was very scary," teammate Daniel Turner told AAP.
"You never like to see anyone like that, especially one of your teammates. But I saw him after the game and he seemed in good spirits and he seemed fine, so hopefully he's all good."
Melbourne coach Steven King confirmed the Demons believed Petty had likely suffered delayed onset concussion from an earlier incident.
"We're still having a bit of a look at that. It was potentially a bit of the delayed concussion or something. So we'll do the right tests," King said.
"We're not 100 percent sure yet, but he was complaining of some blurred vision.
"So we'll do all the tests tonight and tomorrow and I'll let you know as soon as we find out. But obviously, not great."
King said Petty felt he probably should have stopped the game before taking the kick-out, but hadn't felt any symptoms prior to then.
"So whether it was anything else more sinister, whether it was delayed concussion, we'll have a look at it," King said.
"We're obviously going to take it pretty seriously and we'll do the due diligence to make sure he's OK."
Answerth was concussed in the fourth quarter after he was bumped by Demon Kysaiah Pickett into Brody Mihocek, with his head hitting the Melbourne forward's shoulder.
He failed a head injury assessment (HIA) called by the AFL review centre (ARC).
"I was a little bit surprised when he came off and they told me that he was in the protocols, in the ARC," Fagan said.
Answerth was playing his first game back after missing two games with concussion.
"He's had a few concussions, yeah, so we're in the lap of the gods on that one," Fagan said.
"The main thing is what's good for his health."
When asked if he was concerned it could be a long lay-off, Fagan said: "I don't know.
"It'll all depend how he responds, I guess ... the AFL can ask for extra tests and things like that, so I don't know whether Noah will become one of those people that go into that category or not, so we'll just have to wait and see on that."