Section 4: Players & Officials
Rule 3.2.2 requires every team to have a minimum of nine players in the line-up at all times, occupying the positions of pitcher (F1), catcher (F2), first baseman (F3), second baseman (F4), third baseman (F5), shortstop (F6), left fielder (F7), center fielder (F8), and right fielder (F9). If a team elects to use a Designated Player (DP) under Rule 3.1.3, it must list ten players, with the DP batting for the FLEX (Rule 3.1.6), the tenth player named in the line-up who may play any defensive position without batting.
A starting player who has been substituted for may re-enter the game once, in the same batting position, under Rule 3.1.15 (re-entry); a second re-entry, or re-entry in a different line-up position, is an illegal re-entry (Rule 3.1.7). A replacement player may enter for a player who has been withdrawn due to a bleeding injury under Rule 3.1.23, and a temporary runner may run for a catcher or the pitcher of record once that player is on base with two outs (Rule 3.1.22).
Rule 3.4.3 permits up to two base coaches, each required to remain with both feet within the confines of the coach's box while giving direction to batters and runners. A coach or manager under Rule 3.4.1 is responsible for notifying the Plate Umpire of any line-up change and may not use language or gestures that reflect negatively on players, umpires, or spectators.
Rule 3.6 establishes the umpiring crew: the Plate Umpire has full charge of and is responsible for the proper conduct of the game, decides the fitness of the field, calls all balls and strikes, and determines when a game is forfeited, while Base Umpires assist in enforcing the rules from positions on the field. Under Rule 3.6.6, an umpire's judgment on close plays – fair or foul, safe or out, ball or strike – is not reversible except when it conflicts with the rules themselves.