There is no such position in baseball. The running back position is used in American football.
This position is called short stop.
Shortstop
the line
1
The "keystone" in baseball usually refers to second base. It's called such because it is important in scoring (since a runner on second is in "scoring position") and because it's a key defensive position.
Pitcher
Right field.
YES
Position
Catcher
The position abused by steroids in base ball are batter, and thrower.