Rejuvenated by a switch from fullback to the centres, Mitchell was arguably the most devastating player through his first nine games of 2026, scoring 11 tries and registering seven assists.
But after a round-11 loss to the Dolphins, the 29-year-old has failed to return to the field.
First a back injury, which ruled Mitchell out of State of Origin, sidelined the two-time premiership winner, who then picked up a subsequent calf issue.
Mitchell has failed to complete a full season throughout his seven years at Souths.
"Two to three weeks," Bennett said on Friday when asked for an update on Mitchell's likely return date.
The Rabbitohs face Melbourne, Cronulla and Parramatta over the three rounds that follow Saturday's trip to take on Canberra.
Winger Alex Johnston (calf) returns, as does five-eighth Cody Walker after serving a one-game ban for kicking Penrith's Jack Cogger.
Bennett has also opted to stick with journeyman Matt Dufty at fullback and retained Jye Gray on his bench.
Gray came on and filled in on the wing in last week's win over Newcastle, while Dufty set up three tries.
"Jye is a wonderful player for us so it's a balancing act for us at the moment," Bennett said.
"I don't like leaving him out and I don't like leaving Dufty out. Dufty did what we wanted him to do last week and set other players up and I'm sure he can do that again.
"He (Gray) did a great job and he was probably our best player in the end and if he doesn't do that we don't win that game."
Canberra have beaten Souths in their last five meetings and are looking to string three-straight wins together for the first time this season.
Ricky Stuart's side recorded their biggest victory of 2026 in last week's 40-16 demolition of Canterbury, that kept their slim hopes of a top-eight finish alive.
