If Lynch, Tarrant and Gibcus are all injured for R1 I'd be quite worried tbh.
Jack will get a bath from the Carlton backline at his age and we would be left with an undersized backline ourselves against McKay.
Broad is the same height and weight as Curnow.
Miller can pinch hit back there if need be.
I don’t think playing without Tarrant is catastrophic
Broad is considerably lighter, and that's after Curnow lost weight over summer. He had nearly 10kg on broad last year and it's about half that now still.
Not saying it's a catastrophe without Tarrant but Grimes wasn't great last year, coming off a hammy, Balta not amazing either but probably our only realistic option for McKay. If either of their guys have a good night there will be precious little options to move the magnets etc.
Miller has looked consistently better as a ruck/forward IMO but agree is an option.
Also further to my point about Lynch, if he's not out there then Jack will get toweled up comfortably IMO. But he seems likely to play.