I am also betting on a hyperextension of the left elbow, too. In super slow motion, that elbow bent way too far the wrong way. If it is a subluxation, I suspect he may end up getting the same surgery as Bellinger and that means significant time on the IL.
I tried to put off surgery on mine and dragged it out for nearly two years. First injured it in a pick up touch football game. Receiver was about 6'4" to my 6' and had a half step on me down the sideline. I jumped up to bat the ball away and my right triceps came squarely down across his shoulder. Apparently my tolerance for pain is not as high as Newport's, because I was on the ground writhing in pain and rolled over and it popped back into place. There was immediate relief from the sharp pain, but a dull ache remained for a couple of weeks and lifting the right arm was painful for a few days. I had it pop out literally dozens of times with any kind of backward arm motion but could always get back in joint within seconds. Finally succumbed to surgery, which made me a first baseman due to lack of shoulder mobility.