Lee Shelby vs Evgeny Gradovich......why is Shelby a huge favorite???

Nice stacked card you guys have across the pond this Saturday. I am really interested as to know why is Lee Shelby such a huge favorite against Gradovich?? I've seen clips of Shelby, the kid looks like he has a promising future but don't you think that his team has bitten off more than they can chew?? Gradovich is no slouch and is a live dog, a friend of mine told me that Shelby has never been in with a fighter like Gradovich instead he's been feasting on domestic competition and that Gradovich is going to beat Shelby easily. So can my UK boxingscene family please give me more of a insight on Shelby and why is he such a favorite against the tested IBF champ?? Shelby -300 Gradovich +250 Is there something that Bookies know? I know it will be hard for Gradovich to win a decision but is there something that I'm missing??