Is there is another, harder tuber sitting on top of the original rotten-looking one? If so, just break the rotten one away from the harder one discard it, cut off the leaves of the hard one, and you'll be OK. In years past, and this year as well, some of my ee's have done the same thing and I haven't lost one yet.

My EE made lots of much smaller tubers. (original:coconut size, new ones, tennis ball size or smaller. Will they still make it? How do you store them anyway? Warm basement okay?

Cool and dry is best.