Biggest in-house threat: Vitor Belfort.

Belfort is the only middleweight with the stand-up skills to worry Silva. With his blazing speed and explosiveness, Belfort returned to the UFC with a vintage stoppage of Rich Franklin at UFC 103, showcasing the Mike Tyson-esque quality that has made him a fan favorite for more than a decade. Belfort’s physical strength and ground game also give him a great chance, as he does not necessarily have to bank on a stand-up fight to win. How he will adjust if he cannot dictate to Silva remains the wild card. That and Belfort’s extremely dangerous striking make this a compelling matchup.

Acquisition you’d love to see: Outside of Dan Henderson, not a single middleweight ranked in the top 10 outside the UFC presents a credible threat.

Henderson -- rumored to be flirting with Strikeforce -- still has the tools to give Silva problems. With that said, Silva has proven so cool under fire that he consistently works his way out of trouble. Henderson’s opening round against Silva was a masterpiece at UFC 82, but the two-time Olympian still came up short.

Who’ll turn the trick? While the prospect of an unlikely upset remains a possibility with which every champion has to deal, Silva has one of the best chins in the game, so it remains a remote chance at best someone -- outside of Belfort, at least -- will catch him with a fight-changing shot from which he cannot recover. More likely, the fighter to eventually dethrone him will be someone fighting him as Randy Couture did against Chuck Liddell in their first encounter. It will require a perfect game plan, implemented against the smallest margins of error.