Human beings cannot do this. Physically, they can not do this.
Almost 100% of the time the "reaction time/instincts" grade a scout puts on a player is a combination of their hands and raw athleticism as these are much easier to evaluate. It's about as well defined case of attribute substitution as you'll ever find (http://en.wikipedia.org/wiki/Attribute_substitution).
Scouts cannot grade reaction time and therefore they cannot grade range. And since range is far and away the most important factor in a player's ability to create outs defensively, defensive scouting reports are, at best, useless. At worst, harmful and drive bad decisions.
Intellectual dishonesty at it's best. Do you really think a human being can track the path of a pitch better than automated systems like PitchFX, Trackman et al? This can't actually be what you think.
As far as the injury stuff is concerned, how on Earth do you figure that something in this realm will show up in real life but not on video? Explain this to me now.
And keep in mind, you're making the laughable mistake in thinking that MLB clubs only have the video provided by broadcasts. That's obviously not true and they have hours and hours of footage from multiple cameras for each game.
More ********.
You're being completely fooled by randomness. We don't need some low IQ, half in the bag idiot who's fighting off senility on one hand crafting up narratives as to why a player might be 1 for his last 10 in the other. There is literally no explanation required. Again, if it was something obvious, it would most definitely show up on video.