On The Ball
Meaning
To be on top of a situation; in control.
Example
If you were a bit more on the ball, we might have averted the reactor melt down.
Origin
The ball in this instance is a baseball and the on is the spin which the pitcher applies to the ball in order to make it curve during flight. On a good day there will be lots of spin and curve to confuse the batter. The pitcher is said to be on the ball. The expression first appeared in print in 1912 and was clearly in use before then.