JUPITER, Fla. — Before the first official workout of spring training begins, Cardinals coaches have worked backward from how they want it to end. This year it could be vital to how well they start the regular season. The Cardinals are considering a six-man rotation to open the year because of the demands those opening weeks of the schedule will put on the pitching staff. They’ve not committed to it, officials said, and they intend to get some feedback from the pitchers who are committed to routines. But as camp began Wednesday with the first official workouts for pitchers and catchers, the Car…