That discoloration of the inner bladder is a bit concerning, I would consider replacing it sometime in the near future. When it starts to turn brown/orange like that it generally gets stiffer and can become prone to punctures and abrasions.
But to answer your question, that bladder cover is probably still able to be patched. If it were much further I'd say it might not be salvageable but I think you caught it in time. I'll check with Susan in our Service Department, I always defer to her opinion on sewing related repairs. The problem with the unraveling you're seeing here is that even with a patch sewn over it it will likely continue unraveling underneath and poke out underneath the patch eventually. That's part of why we have that heat sealed circle around the opening.
I have to recommend replacing the bladder cover, but I can tell you what I've seen some folks do to fix this. Heat sealed patches on both sides of the damaged area would keep it all together for a while, although it stiffens up that area and may end up peeling off in the future. Aquaseal is always an option. I've seen some folks try to sew a patch over it, but that is a short term solution as it doesn't address the unraveling fabric underneath.
edit: I saw your post in the BC forum, I understand now this is a backup BC for you. How old is the BC itself? Can you take some pictures of the entire BC and bladder assembly so I can get you the correct part number for that bladder cover and inner bladder?
More edits: Susan pointed out some details in the picture I didn't see immediately, this cover isn't repairable here at the factory. The area unraveling is too wide for the heat seal patches (for lack of a better name) we have and the age of the BC probably means the inside of the fabric wouldn't accept the heat seals we use now.
