Honestly I really don't see how he could lose if he isn't plain stupid. He only needs to get a quick hold of Silva, wich many others have done before him and after that, he would most likely take him out with a quick sub.
In my mind he is just to strong for Silva and way too good on the ground. His Takedowns are nasty as well and he is just so athletic on top of that.
Like somebody mentioned in clinch postion he would lose.. I really find it very hard to believe that. Harris would just pick Silva up and dump him on his head in that postion.
I really think Maia must be the only one who could defend against a guy like PaulHarris. He won't ever submit Harris either.. but he could very well control him on the ground maybe and win a UD. But even here, I think Harris is just too strong and too athletic for somebody like Maia, also the standup could be in favor of Harris as well.