In every professional organization, duties need to be done in every single game. at the Twins we have a pitching chart, a game chart and velocity chart. Each one of these charts is completed by a pitcher who is not pitching on that day. Other duties that need to be done are bat and ball boy, an honour that I've have had bestowed on me twice in the last 4 days, and also someone will be using a video camera during the game.
The pitching chart is used to document our pitchers for the game. Such things that are recorded on this chart are, balls and strikes, what type of pitches were thrown, the location of pitches in an at bat and how the hitter got on base or out. Once you get the hang of it, the pitching chart can be very easy, and very valuable to any pitcher who has the time to study opposing teams lineups. The pitching chart is usually done by the starting pitcher for the next day, so he can get a look at the team he will be facing the next day.
The game chart is much simpler then the pitching chart, and is used to document our hitters for the game. It is almost like doing a regular scorebook. We write down what the hitter did and what the count was they got on base or out. At the end of the game we have enough information to complete an entire box score on our own hitters.
The velocity chart is pretty self explanatory, it just records the velocity of every pitch thrown. People are more interested in this chart then the others, because everyone likes to know how hard they are throwing and whether their velocity is improving.
The least glamourous of these duties is being bat and ball boy. Basically, all you do is run back and forth from home plate all game, picking up bats, foul balls that go towards the back net, and give the umpire new baseballs when he is running low. Also on occasion I would run the umpire a cup of water in between innings, since they are also working hard back there, and if we want them to be at their best, they need to be hydrated as well.
The last duty that needs to performed is having someone on the video camera, the video recorded with the camera is used to see if the pitcher has any flaws in their mechanics, and if the pitching coach notices anything wrong, he would sit you down and show you what is going wrong, or work with you in your next bullpen session.
To someone who doesn't know much about baseball or a fan, these duties may seem very small in terms of playing baseball, but they are an important part of what makes the team, and an individual successful in professional baseball.