Sorry I think I misunderstood your post too, you mean we need to retain a 3rd choice keeper and 4th choice centre back despite them not playing much. You aren’t calling for us to replace the current choices, it appears we are in agreement.
We have 3rd choice in Nikki Maenpaa, a full international keeper. Why the need to replace him? And who could we get better knowing they would be unlikely to get a game (or in the match day squad most of the time).
If Ryan gets injured Krul starts and Maenpaa will be on the bench.
We don’t need another keeper or a 4th choice centre back, the ones we have got as cover will be more than adequate and have been left out because Ryan, Duffy and Dunk have been pretty much unstoppable. Both of our backup keepers are full internationals, not sure we will be able to attack better...