Gawn and teammate Jack Viney collided early in the first quarter of Friday's contest at the Gabba and the ruckman initially ran away from the contest.
But the influential Demons' skipper was no sooner heading to the sideline and, after being subbed out, Gawn cut a forlorn figure as he sat on the floor of the dressing room with his left knee wrapped in ice.
Melbourne eventually lost on an eventful night in Brisbane, the Demons cutting a 40-point margin to 11 by fulltime after a blackout stopped play for 40 minutes.
Coach Simon Goodwin said the club would wait for scans to confirm the extent of his injury, but did not rule out an ACL tear.
"There's an emotional toll to your team when you lose your skipper early in the game," Goodwin said.
"He's got a knee, we need to get it scanned. So we'll just have to wait and see."
Asked about a potential worst-case scenario, Goodwin added: "It'd be unfair to go down that pathway ... we're unsure.
"I don't want his family to be sitting home thinking he's done his knee."
The Demons were smashed in the clearances with Gawn missing, Collingwood recruit Brodie Grundy now preparing to play more minutes in the ruck.
"I thought his second half was pretty strong, he took a big step forward again tonight, Goodwin said of Grundy, who was restricted to six games last season with a knee injury of his own.
"He's going to have to shoulder a bit of responsibility depending on Max, so I'm sure he's the type of ruckman that will relish that opportunity."
Steven May had already been scratched for the Gabba clash, the key defender unable to get up for what was to be his return from a calf injury.
"He's fine," Goodwin said.
"He just missed a couple of his markers during the week that we were pretty keen for him to hit and with his soft tissue history, we just weren't prepared to take that risk.
"He's an important player to us; we want to make sure he's right for the whole season. So he'll definitely play this week."
Earlier on Friday, the club confirmed Christian Salem has suffered another setback, with the defender's AFL return further delayed by a knee injury.
Salem, who was sidelined for more than two months last year because of a separate knee injury, had been on the verge of making a comeback after battling a thyroid issue.
The 27-year-old speedster had been earmarked to play in Casey's VFL match against Footscray.
But he was sent for scans on Friday after experiencing soreness in his left knee and has been ruled out indefinitely with a small tear in his meniscus.
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