Don't think ability is the problem here. Almunia's a decent mid-level keeper for someone, somewhere.
The problem is that he's barely played for 2 years now and sat on his backside showing no ambition to fight or go elsewhere on loan. He's also 35 years old, even for a goalkeeper that's quite close to retirement so why would anyone want to waste him bringing him up to match fitness and building a side around him when there are cheaper and younger alternatives?