"While stepping back" is ambiguous. If F1 legally stepped off with his pivot foot, then he's an infielder and can feint to first. If he "stepped back" in some other sense, then it's a balk.
I'm guessing that you meant to ask simply about the timing: does F1 have to step off before feinting to first? Bob Jenkins answered that question.
__________________
Cheers,
mb
|