Baseball Terms: This Is a Whole New Ballgame

on the ball is intelligent and able to do a good job. But a person who threw a curve ball did something unexpected.  Someone who steps up to the plate is ready to do his or her job.  A pinch hitter takes the place of someone else at a job or activity.

strikes out or goes down swinging attempted something but failed.  We also might tell the person that three strikes and you are out.  But someone who hit a homerun or  hit it out of the park did something extremely well.

right off the bat.  If someone is doing an extremely good job and is very successful, you might say he or she is batting one thousand.  

touch base with you, I will talk to you from time to time about something we plan to do.  I might say I touched all the bases if I did what is necessary to complete a job or activity.  And if I covered my bases I was well prepared.  However, someone who is way off base did something wrong or maybe even dishonest or immoral.  A person with strange ideas might be described as out in left field.

a ballpark figure or a ballpark estimate. 

in the ballpark.  However, if I say we are not in the same ballpark, I mean we cannot agree because my ideas are too different from yours. 

that is a whole new ballgame.