Please explain this obstruction call.
Runner was advancing to third on dropped pitch. Catcher immediately recovered and threw ball to 3rd. Before the ball was thrown, the field umpire signaled obstruction. The runner was about half way to third, when the obstruction was signaled. The shortstop was nowhere near the runner's line. I couldn't tell the third basemen's position from my angle, she may have been in front (between runner and the base) of the bag. However she received the ball when the runner was three steps before reaching the bag. Again the obstruction was signaled before the catcher released the ball and the runner half way to third.