Consider a typical situation when a batsman steps out of the crease against a spin bowler to play an attacking shot. However, the ball turns very sharply (due to pitching into a footmark/crack and/or exceptional skill of the bowler), and hits the short leg or silly point fielder (not his helmet), then ricochets on to the stumps. The ball hit the fielder before it crossed the batsman. In such case, would the batsman be run out?
Of course, if the fielder deliberately "snatches" the ball, it would be considered as significant movement distracting the batsman, and the umpire would call no ball. However, if it happens accidentally, this won't apply.
See below illustration.
.....+-----SSS-----+ S - stump .....| @ | B - batsman .....+-----@-------+ F - fielder .....| @ | @ - ball trajectory .....| @ B | ....@| | ..F..| | ....@| | .....| @ | .....| @ | .....| @ |