It takes about one year to recover from a broken/fractured ankle. Also remember, Karlsson didn't even get training in. on top of that, Ottawa sucks and their owner sucks more, so i'd argue it's a mixture of all of that vs. Karlsson's original injury or him being the same again.
Unless you are suggesting that we just shut down Matthews period, he's okay to play. I doubt anyone right now is healthy, and one good bump could take someone out. he'll be fine, he'll probably need some surgery to clean out the shoulder or something. I don't think/doubt it will be chronic, and even if it was, we have the staff involved to make sure it doeesn't flare up.