Legal guarding position on a fast break

Basketball Officiating Calls
Does the defender have a legal guarding position and maintain it during this play before contact?

[jeffwright]

Looks like a good call to me, but I think the C had a better look at it than the L, plus it is squarely in the C's primary. So, not sure why the L put a whistle on that.

[danroberts]

This is an easy player control foul. Legal guarding position was established at mid court. Defender backpedaled and moved laterally to keep LGP. Has to be a player control foul, otherwise ask yourself what did the defender do wrong?

[djshepherd]

I thought good call at first too, but then it looks like the defender takes a step toward the attacker when he makes his side step. His right foot appears to go forward. I probably would've called an offensive foul here, but then saw the film and thought that I'd missed it. It isn't much, but it definitely looks like a step towards at 51.3 seconds on the clock.

[JohnCarterRocks]

Dribblers head and shoulders were past the mid point of the defender. Block.