The news is not good, however, for Port Adelaide captain Tom Jonas and GWS veteran Callan Ward, who have been handed one-match bans by AFL match review officer Michael Christian for rough conduct.
Jonas was involved in a head clash with West Coast's Jai Culley and was ruled responsible for the incident after electing to bump his opponent.
It was graded careless conduct, medium impact and high contact, leaving Jonas set to miss the Power's huge date with ladder leaders St Kilda on Friday night.
Ward was cited for his sling tackle on Lachie Neale, whose head bounced into the ground while he was in a vulnerable position.
The incident was graded careless conduct, medium impact and high contact, and Ward is set to miss the Giants' derby with Sydney on Saturday.
Duncan is free to play against Essendon on Sunday after an unusual incident when Fox ran past a loose ball during Saturday night's match at GMHBA Stadium.
Duncan braced for contact and made high contact with Fox, but Christian ruled the Geelong midfielder's actions were not unreasonable.
"Fox approaches from the opposite direction and attempts to knock the ball forward," the AFL explained in a statement.
"In doing so, Fox runs past the ball and lowers his body position before contact is made with Duncan.
"It is the view of the MRO that Duncan's actions were not unreasonable in the circumstances. No further action was taken."
Geelong coach Chris Scott told reporters post-match he expected Duncan to be cleared.
"I looked at it really closely and it's almost impossible to do anything different to what he did when a player is coming at you at that speed," Scott said.
"I am not saying Fox deliberately ran past the ball but he ended up past the ball and Mitch has got to protect himself somehow."
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