Bathroom subfloor damage

[BrianDickens]

First of all, sorry if I use the wrong terms as I describe my problem. I'm fairly new at this.

So, I am currently in the process of renovating my bathroom and I found something that makes me a little nervous. The floor used to be 1" tile on top of poured concrete with wire mesh backing. I have pulled all of that up and I'm down to the plywood subflooring. I plan on putting down backerboard and then ceramic tile on top of that.

The problem is best illustrated by photos which I am including here.

If the damage at the tub didn't seem so extensive, I'd just put down the backer board and be done with it. However, the extent of it frightens me a bit. Will it be okay if I leave it? Is there something I can fill it with before putting down the backer board? Should I try to replace the plywood (this is likely to involve removing the tub which I do not want to do)?

Any help would be appreciated.

Thanks

[BrianDickens]

I can take more pictures if it helps.

[HayZee518]

If the wood is "punky" around the tub then rest assured its waterlogged underneath. best take out the tub and re-do the whole sub floor. I'm sorry it comes to this. Water travels in the most obscure places and causes problems. concrete board will not solve the problem. it'll makes the floor hard again but the sub floor is still springy.

[ceramictilepro]

water damage areas need to be looked at and fixed to prevent any further damage. there is no shortcut unfortunately

ceramictilepro