Although Ryan hasn't experienced any health issues this spring, his velocity has dropped from 89 m.p.h., where it sat last year, to the mid 80s. It's worth mentioning that even last year was a slowdown from his pre-Tommy John surgery days, when he would routinely reach 92. That's unusual for a pitcher returning from ligament replacement surgery - in fact, pitchers who recover sometimes find their arm is actually stronger.
People are speculating that Ryan will need to begin the season on the DL, and are comparing it to Brandon League's showing two seasons back, when he showed up almost 10 m.p.h. slower than he had been the season before. League began the season on the DL and had to work his way back, and it took quite a while.
Pitch velocity is about mechanics as much of more as it is about arm strength. Most of how fast you throw is how fast you can move your arm, and that's largely a function of mechanics. Of course, grip is also a large function of that. Ptichers reach their peak velocity by devleoping delivery mechanics and then repeating those mechanics to the fullest extent possible.
We know that Ryan is having mechanical problems as that was the reason he missed the WBC, so it sounds like he's still working out those mechanical issues. That's more likely than some sort of hidden arm injury. That said, bad mechanics often leads to injury.
As of now, it all remains very mysterious, but we will keep you posted.