Everyone has made some valid points, and it is interesting they way the wind shifted direction by the second page of responses.
This type of situation is definitely, "had to be there", material.
Personally, I have always protected the fielder on a direct path to field the ball, and at the point where they are fielding the ball. But if their momentum carries them past that point of fielding the ball, I haven't protected them. And it this situation, that is what happened. I mean, how far do you allow the fielder past the point of fielding the ball, protection ?