Lissah is probably the only viable option. I would even suggest that Galbraith covers right back before Key.
Luckily due to no real injury issues last season, Christie and Tjoe a On only had the game time you lost above.
I would hope Santos comes in as the Christie/Naughton replacement, we then look at a CB to cover Cabango/Burgess and a loan LB to cover Tymon.
Guaranteed if we go thin defensively then we will get caught out with injuries, as we have done this pre season......if that's not a warning then I don't know what is.