Here's a cue that sometimes help.
When the front foot plants (down), that back arm better be up or you are going to rush things.
I've had pitchers be up in the zone also because they were using a slide step which was affecting the timing of the hand break where they weren't getting the arm up fast enough and were then rushing to the plate leaving everything up.
I suggest knee to knee like Steve advocates. Hold the runner on by changing up 1 to 3 seconds and stepping off and use a knee to knee. I'm not an advocate of the slide step due to seeing what it can do to timing.