The fielding side consists of (a) the pitcher and catcher, called the battery, (b) the first-baseman, second-baseman, third-baseman and short-stop, called infielders, and (c) the left-fielder, centre-fielder and right-fielder, called out-fielders.

The pitcher, who delivers the ball to the batsman, is the most important member of the side. In the act of pitching, which is throwing either over or underhand, he must keep one foot in contact with a white plate, called the pitcher's plate, 24 in. long and 6 in. wide, placed 60.5 ft. from the back of the home-base. Before 1875 the pitcher was obliged to deliver the ball with a full toss only, but about that time a disguised underhand throw, which greatly increased the pace, began to be used so generally that it was soon legalized, and the overhand throw followed as a matter of course. As long as the arm was held stiff no curve could be imparted to the flight of the ball in the air, but with the increase of pace came the possibility of doing this by a movement of the wrist as the ball left the hand, the twist thus given causing the ball, by the pressure on the air, to swerve to one side or the other, or downwards, according to the position of the hand and fingers as the ball is let go. The commonest of these swerving deliveries, and the first one invented, is the out-curve, the ball coming straight towards the batsman until almost within reach of his bat, when it suddenly swerves away from him towards the right, if he be right-handed. The other important curves are the incurve, shooting sharply to the left, and the drop, with their many variations, nearly every pitcher using some favourite curve.

Change of pace, disguised as well as possible, is also an important part of pitching strategy, as well as variation of the delivery and the play upon the known weaknesses or idiosyncrasies of the batsman. Good control over the ball is a necessity, as four "balls" called by the umpire, - that is, balls not over the base, or over the base and not between the shoulder and knee of the batsman, - entitle the batsman to become a base-runner and take his first base. If the pitcher disregards the restrictions placed upon him by the rules (e.g. he may not, while in position, make a motion to deliver the ball to the batsman without actually delivering it, or to first-base, while that base is occupied by a runner, without completing the throw), he is said to have made a balk, which permits a base runner to advance a base. In fielding batted balls the pitcher takes all that come directly to him, especially slow ones which the other fielders cannot reach in time. One of his duties is to "back up" the first-baseman in order to stop balls thrown wide, and to cover first-base in place of the baseman whenever that player has to leave his base to field a ground ball.

On occasion he also backs up other positions.

The catcher usually stands about 1 yd. behind the home plate, and he must never be more than 10 ft. behind the home plate when the pitcher delivers the ball to the batsman. He generally catches the ball from the pitcher before it strikes the ground, and, when a man of the opposing side has succeeded in getting to a base, must be on the alert to head this opponent off should he endeavour to steal the next base, i.e. run to it while the pitcher is delivering the ball to the batsman. For this reason the catcher must be a quick, strong and accurate thrower. As the catcher alone faces the whole field, he is able to warn the pitcher when to throw to a base in order to catch a runner napping off the base, and by secretly signalling to the pitcher (usually by means of signs with his fingers) he directs what kind of a ball is to be pitched, so that he may be in the proper position to receive the ball, be it high or low, to left or right. Some pitchers, however, prefer to reserve their choice of balls and therefore do the signalling themselves.

The catcher wears a mask, a breast-pad, and a large glove, without which the position would be a very dangerous one.

Base ball Field. Diagram of Base-ball Field.

As every batsman upon hitting the ball must run for the first-base, the first-baseman must be a sure catch of balls thrown to head runners off, even those thrown too low, high or wide. A tall man is usually chosen for this position. The second-baseman usually stands about 30 ft. to the right of second-base and back of the line between the bases, and attends to balls batted to his side of the diamond. He also backs up any exposed position and must be ready to cover second-base whenever a runner tries to steal down from first-base, or whenever there is a runner on second-base, a duty which he shares with the short-stop, whose position corresponds to that of the second-baseman on the left side of the diamond. Short-stop must be a quick and accurate thrower and a lively fielder, as he is required to back up second- and third-base. Both he and the second-baseman must field ground balls cleanly and are often called upon to catch fly balls also. The requirements of third-baseman are very similar, but he must be an exceptionally good thrower, as he has the longest distance to throw to the first-base; and as he plays nearer to the batsman than do the second-baseman and the short-stop, the balls batted in his direction are apt to be faster and more difficult to field.

One of the third-baseman's chief duties is to be ready to run in towards the batsman to field "bunts," i.e. balls blocked by allowing them to rebound from a loosely held bat. These commonly roll slowly in the direction of third-baseman, who, in order to get them to first-base in time to put the runner out, must run in, pick them up, usually with one hand, so as to be in position to throw without the loss of an instant, and "snap" them to the first-baseman, i.e. throw them underhand without taking time to raise his body to an erect position. Many of these bunts can be fielded either by the pitcher or, if they drop dead in front of the home-plate, by the catcher. The positions of the three outfielders can be seen on the diagram. Their duties consist of catching all "flies" batted over the heads of the infielders (i.e. high batted balls that have not touched the ground), stopping and returning ground balls that pass the infield, and backing up the baseman. The accompanying diagram indicates the territory roughly allotted to the different fielders. "Backing up" is a very prominent feature in fielding.