It is my personal belief that an umpire should not change a call based solely on his judgement ever.
Now let me qualify that.
Check swings are obvious cases where the BU can reverse the PUs call.
In the case of a pulled foot/swipe tag on the BR going into 1st, I think the BU should go to the PU for confirmation
before making the call if the subject was discussed in the pregame meeting.
All other calls which are based on judgement alone cannot and should not be reversed, especially if they occur during on going action. This has everything to do with avoiding "what-if" games and nothing to do with umpires egos. If you blow a call during on-going action you are stuck with it since the call you make will normall effect subsequent action. The best you can do is to get in position for every play, focus on the play until the action is complete, and make the best call that you can; then live with it.
Finally for those who don't read the BB board, the five situations where a call can be changed are:
- Two umpire make opposite calls on the same play.
- Check swing.
- An umpire misinterprets a rule.
- A call of fair is changed to foul or a home run becomes a double (also vice versa).
- A ball comes loose on a tag for an out, and another umpire sees it.