Fielding Team

The team in the field is the defensive team; they attempt to prevent the team at bat from scoring. There are nine defensive positions, however, only two of the positions have a mandatory location (pitcher and catcher), the locations of the other fielders is not specified by the rules. These fielders often shift their positioning in response to specific batters or game situations, and they may exchange positions with one another at any time. The nine positions are: pitcher, catcher, first baseman, second baseman, third baseman, shortstop, left fielder, centre fielder, and right fielder.

The Battery

The battery is the pitcher, who stands on the rubber of the mound, and the catcher, who squats behind home plate.

The pitcher's main role is to pitch the ball toward home plate with the goal of getting the batter out. Pitchers also play defence by fielding batted balls, covering bases (for a potential tag out or force out on an approaching runner), or backing up throws.

The catcher's main role is to receive the pitch if the batter does not hit it. Together with the pitcher and coaches, the catcher plots game strategy by suggesting different pitches and by shifting the starting positions of the other fielders. Catchers are also responsible for defence in the area near home plate.

The Infielders

The four infielders are the first baseman, second baseman, shortstop, and third baseman. The first and third basemen play near their respective bases. The second baseman and the shortstop position themselves in the gaps on either side of second base, toward first and third base, respectively. Originally, the second baseman played very close to second base; this positioning shifted when teams found it necessary to have four infielders, rather than four outfielders.

The first baseman's job consists largely of making force plays at first base on ground balls hit to the other infielders. The first baseman also fields balls hit near first base, but because the position is less demanding than the others, the team's strongest hitter is often also their first baseman.

The second baseman covers the area to the right of second base and provides backup for the first baseman.

The shortstop fills the critical gap between second and third bases - where right-handed batters generally hit ground balls - and also covers second or third base and the near part of left field. This position is the most demanding defensively, so a good shortstop need not necessarily be a good batter.

The third baseman's primary requirement is a strong throwing arm, in order to make the long throw across the infield to the first baseman. Quick reaction time is also important for third basemen, as they tend to see more sharply hit balls than the other infielders.

The Outfielders

The three outfielders, left fielder, centre fielder, and right fielder, are so named from the catcher's perspective (from home plate looking onto the field).

The right fielder generally has the strongest arm of all the outfielders due to the need to make throws on runners attempting to take third base.

The centre fielder has more territory to cover than the corner outfielders, so this player must be quick and agile with a strong arm to throw balls in to the infield; as with the shortstop, teams tend to emphasise defence at this position. Also, the centre fielder is considered the outfield leader, and left- and right-fielders should cede to their direction when fielding fly balls.

Defensive Strategy

Pitching

Effective pitching is vitally important to a baseball team, as pitching is the key for the defensive team to retire batters and to preventing runners from getting on base. A full game usually involves over one hundred pitches thrown by each team. However, most pitchers begin to tire before they reach this point. In previous eras, pitchers would often throw up to four complete games (all nine innings) in a week. With new advances in medical research and thus a better understanding of how the human body functions and tires out, pitchers tend to throw fractions of a game about every five days.

Multiple pitchers are often needed in a single game, including the starting pitcher and relief pitchers. Pitchers are substituted for one another like any other player, and the rules do not limit the number of pitchers that can be used in a game. Relief pitchers were uncommon in baseball's early years, with the starter normally remaining for the entire game; today, over the course of a single game, each team will most commonly use two to five pitchers.

Although a pitcher can only take one step forward while delivering the ball, the pitcher has a great arsenal at their disposal in the variation of location, velocity, movement, and arm location. Most pitchers attempt to master two or three types of pitches; some pitchers command control over up to 6 types of pitches. Common pitches include a fastball, which is the ball thrown at a maximum velocity; a curveball, which is made to curve by rotation imparted by the pitcher; and a change-up, which is a slower version of a fastball.

To illustrate pitching strategy, consider the "fastball/change-up" combination: The average major-league pitcher can throw a fast ball around 90 miles per hour (145 km/h), and a few pitchers have even exceeded 100 miles per hour (161 km/h). The change-up is thrown somewhere between 75 to 85 miles per hour (121 to 137 km/h). Since the batter's timing is critical to hitting a pitch, a batter swinging to hit what looks like a fast ball, would be terribly fooled (swing and miss, hopefully) when the pitch turns out to be a much slower change up.

Some pitchers choose to throw using the 'submarine style,' a very efficient sidearm motion. Pitchers with a sidearm delivery are often very difficult to hit, but can be erratic with control of their pitches.

Fielding Strategy

Since only the pitcher and catcher location is fixed, the other players on the field move around as needed to defend against scoring a run. Many variations of this are possible, as location depends upon the "situation." "Situation" refers to immediate circumstances of play, and includes: