Port Adelaide fear captain Domenic Cassisi has suffered a sinus fracture which could keep him out of the club's push towards the AFL finals.

Cassisi was hurt during a nasty clash of heads with Hawthorn's Jordan Lewis at AAMI Stadium on Sunday, but returned to the field with his head bandaged and helped the Power win the game.

That victory put Port into the eight with four rounds remaining, but they might be without their inspirational skipper if scans on Tuesday confirm the worst.

Port ruckman Dean Brogan said Cassisi's courage to return after the knock typified the midfielder's mettle.

"That's Dom for you," Brogan said.

"People sort of questioned why he was made captain at the start of the year, but he has put that to rest now.

"He's a fantastic leader.

"We're not sure where he's at at the moment, but for him to come back on after a serious knock just sends a message to the rest of the group.

"If you don't follow his lead, you're going to get left behind."

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