Fake to Third / Throw to First

[cmcramer]

Can't remember this one, although I 've read it in past years here...

With runners on first and third, a right handed pitcher executes the 'double move' - fake a throw to third, pivot and throw to first. This particular pitcher's stride toward third was very short, his fake throw was quick and not convincing, and his pivot to first was on a right foot that never left the rubber!

Does the right foot have to leave the rubber for this move to be legal?

Thanks!