In other big round-16 selection news, the Eagles have lost Tim Kelly to a hamstring injury, Port have dropped Todd Marshall again, while Andrew McGrath and Darcy Parish are among the reinforcements at Essendon.
Darcy started the season as the Dockers' preferred ruck partner to Luke Jackson, before being grounded by concussion and calf issues.
Cox, a premiership winner at Collingwood who moved to Fremantle at the end of last year, has played the past nine games of the Dockers' current 13-match winning streak.
But with averages of 6.5 possessions and 13.8 hitouts per game this season, Cox hasn't done enough to hold his spot, especially with Darcy impressing in recent WAFL outings.
The Suns have lost Sam Clohesy (suspension) and Daniel Rioli (broken jaw), but could be boosted by the return of defender Wil Powell (shoulder).
The Blues, riding a five-match winning streak under interim coach Josh Fraser, are taking no risks with Weitering's calf injury ahead of Saturday's meeting with West Coast at Marvel Stadium.
"We're more than comfortable (with how we've approached the injury)," Fraser said before the teams were released on Thursday night.
West Coast have lost midfielder Kelly to hamstring tightness and axed defender Josh Lindsay for the second time this season.
Jack Graham returns after recovering from shoulder surgery, while No.1 draft pick Willem Duursma (calf), Tom McCarthy (hamstring) and Jack Hutchinson (hamstring) are also back.
Port have axed Marshall again on top of losing Esava Ratugolea to a serious knee injury as part of five changes for Saturday's Showdown with Adelaide.
Brownlow Medal winner Ollie Wines and Brandon Zerk-Thatcher are among the ins for Port, while the Crows get back Josh Worrell and Isaac Cumming, but lose Wayne Milera (hamstring tightness).
Essendon have loaded up their extended squad, naming McGrath, Parish, Isaac Kako, Jye Caldwell, Tom Edwards and Saad El-Hawli as potential ins for Sunday's match against North Melbourne.
Bombers duo Kyle Langford and Archie Roberts have been ruled out with injury, while Kangaroos ruckman Tristan Xerri is out with a broken jaw.
GWS have replaced Jesse Hogan (finger) with Max Gruzewski for Friday night's crunch clash at the MCG, with Hawthorn losing Jarman Impey to injury and Josh Weddle to suspension.
Collingwood welcome back games record-holder Scott Pendlebury against Richmond on Saturday, with the Tigers boosted by the return of forward Rhyan Mansell (foot, wrist) and Jack Ross (concussion).