As a Leafs fan, we do have a long history of signing guys in their late 20s or older, who have a long history of health problems, and are very risky signings. Klingberg, Murray, Kase, Connolly, Lombardi, etc. Sometimes it sort of works out, often it's a complete failure, and I can't really think of any case, off the top of my head, where it's been a great move. Maybe I'm forgetting someone, though.
Obviously they think he's healthy enough to be an effective player this year, or they wouldn't have signed him. Whether or not they're right is very much TBD.