Based on the episode preview they posted, it's starting to make sense. The Rebels crew will run into him on Geonosis. The empire sterilized that entire planet (to keep the Death Star secret) by using some kind of chemical insecticide on the planet that killed them. If Saw was there, that insecticide may be why his lungs are all messed up and he has to use that breathing tube, and it may have messed up his mind.