[mbyron]

The fielder is protected doing everything normal to field a batted ball, including charging it and waiting on it. The fielder fielding a batted ball has the "right of way," and the runner must avoid contacting him (not just try to avoid contact). Even accidental contact is interference. The protection ends when the fielder has finished fielding (could be a catch, a tag attempt, or a throw, and perhaps other things).

The only way I could see interference NOT being called in this type of case would be one where the fielder intentionally throws himself at the runner to draw the interference call. I've never seen it or heard of it happen, but I'm sure that someone around here has!