Harrison Petty was feeling fine before he marked the ball on the last line of defence at the MCG on April 19. Seconds later, the 26-year-old said the ground was spinning around him, his vision blurred and his kick sprayed off the side of his boot, with Will Ashcroft punishing the mistake with a goal.

Petty went down on one knee and was helped from the ground by Ed Langdon, Xavier Taylor and Blake Howes, before Demons doctor Jacob Jewson and physio Zach Nelson got him off the field. His day ended just before three-quarter time in round six, and the scene immediately set off concern because he has had multiple concussions in the past.

What followed was a battery of tests and specialist visits later in the week, including assessment from a neurosurgeon, a dizziness expert and a cardiologist. The diagnosis was eventually a vestibular migraine, not concussion, and Petty returned to play a fortnight after the incident.

Petty said he had never had a migraine before April 19, which made the episode more confusing at the time. He said migraines run genetically in his family, with his brother, sister and grandparents all getting them badly, something he did not know until after the MCG scare. “I was very confused myself, because I’ve had my fair share of concussions in the past, but it never really felt like a concussion,” he said, adding that the later tests showed it was a migraine or vertigo rather than a head knock.

The forward-defender has now played two games since the incident and has resumed his return to defence under new senior coach Steven King and new backline coach Jared Rivers. Petty said he grew up playing as a defender, spent a few years being injured and is happy to do anything for the team, including moving forward if needed, but he would also like to settle somewhere and build continuity in his game.

That next stretch matters because the MCG episode could have easily pushed Petty back into the uncertainty that has followed him at different points in his career, only this time the specialists cleared him and he is back in the role he knows best. For Melbourne, the question now is not whether he can keep playing, but how quickly he can turn a frightening afternoon into a stable run in defence.