Really silly question: what makes you suspect they might not be legit? Does the vendor of the ticket smell fishy or was your method of obtaining the ticket a bit fishy?

I'm not passing judgment - I've certainly bought sporting event tickets off of illegal scalpers where, in the back of my mind, I've wondered "Are these fake?" I knew the risk was there but I still went through with the buy. I'm just curious as to the source of your concern in this case.