Selwyn Cobbo, who would have played wing if Walsh was fit, trained at fullback and will wear the No.1 jersey in Penrith on Friday night.
Jesse Arthars is set to be the new winger. Walsh trained with a no-contact red bib on Monday but the Broncos have decided to err on the side of caution.
Walsh's absence continues a difficult week for Brisbane, with centre Herbie Farnworth and prop Tom Flegler committing their futures to the Dolphins from 2024, a scenario Carrigan said was "tough" to take.
Carrigan said the dynamic Cobbo would fill the No.1 role against the Panthers with aplomb.
"Walshie is not quite ready to go. It is 27 rounds and we will rest him up," Carrigan said.
"Cobbo can do things that no-one else can do and Walshie can do things no-one else can. We are pretty lucky that the number one and two up-and- coming fullbacks in the game are at our club.
"I am excited for Jesse. In the Maori All Stars and last week for us (in the trial win over the Cowboys) he was one of our standouts."
Carrigan said the NRL was "a bit like a business" and that he didn't begrudge Farnworth and Flegler leaving, but added he had not expected them to do so.
"It is tough," Carrigan said.
"They are two of my close mates and when you come through together as kids you never really expect them to leave.
"I am hanging out to have a really good year and send those two off, and (Gold Coast-bound) Keenan (Palasia). Hopefully we can end this year with a premiership."
Carrigan said he expected the Dolphins would continue to pose a threat to the Broncos as players looking for starting positions no longer had to uproot their lives to move to Sydney.
"It is a challenge, but it is a luxury for some of these guys too that have got different family situations," he said.
"A powerful new club has come in with a powerful history and if they can secure a good deal and look after themselves ... I can't begrudge that."
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