If he's not fit, Mayne should sit this one out. I can see why he'd be reluctant to though. If Crozier comes in and plays a blinder it's going to be damn hard to win a starting 22 spot back.
I believe that is exactly what played out last year when Chopper played against Sydney at the SCG. The game Josh spat the dummy over.
Mayne definitely carried an injury into that match.
I reckon if Josh had gone to the airport, he would have played; Most likely at the expense of Mayne.