I only have one Gretzky auto, so by no means am I qualified to authenticate his signature, but I have seen a lot over the years, and it appears it could be something he may have rush signed at a golf tournament, or something like that? If it is fake they did a decent job copyng it, IMO. Might be worth sending it to PSA, and have it slabbed, and to see what they think?
Checked his current sales, and sold items, and he has a lot of Jordan, Tigers, Kobe's IP etc. Either he's a hound, or an artist. The Tiger autos look pretty close to what I had in my collection. Who knows? When you buy stuff like this it's a big risk, and not one I would chose to take, but that's me.