This card was not signed as part of the set, it was originally pulled unsigned and autographed at a later date. To my knowledge, Erik Karlsson does not do many in person or TTM autos. At the time of this writing, it appears that he also has yet to have an Upper Deck Buyback Young Guns auto released.
The above makes it very difficult to obtain his Young Guns card with a clean authenticated signature. Depending on the final total, signature required and/or do not safe drop may be enabled.