Pedro Strop has a loose, whippy arm action with good velocity to go with it - 93-96 mph heater, 82-86 mph slider, and what appears to be a splitter or split-change as you can see in the picture above.

Readers tipped me off to Pedro through ProspectTube, and the first thing I noticed was that loose arm. However, a more detailed analysis of the video shows that he has classic signs of hyperabduction - Strop takes his elbow well above and beyond the acromial line, which will unnecessarily stress the anterior portions of the shoulder as well as the glenohumeral ligament (tip to seattle_pt1).

However, Strop's injuries are to his elbow - stress fractures at the tip of it, to be precise. Google searches will turn up multiple pages that confirm this, and many sites will say that it is a rare problem. It actually isn't; not for pitchers. "Stress fractures" at the tip of the elbow are olecranon fractures, and they typically occur when you fall directly onto your elbow. However, baseball pitchers are at-risk for this type of injury when they release their pitches with a supinated grip, as they are slamming the olecranon process into its fossa, irreversibly lengthening the ulna bone, irritating the hyaline cartilage, and damaging the UCL.

Here's a clip of Pedro Strop, taken from that YouTube video:

Though it's tough to tell due to the background, if you look carefully, you can see that arm creep up into hyperabduction very quickly.

Pedro Strop has UCL bruising/tears as well, which correlates well with my analysis.

Strop's mechanics remind me a lot of Andy Sonnanstine's:

I think they are both at-risk for similar types of injuries - I would not be surprised to see Sonnanstine go down with an olecranon fracture, though it's a lot more common to see UCL ruptures first.