SP meaning in Sports ?

In baseball (hardball or softball), a starting pitcher or starter is the first pitcher in the game for each team. A pitcher is credited with a game started if they throw the first pitch to the opponent's first batter of a game. Starting pitchers are expected to pitch for a significant portion of the game, although their ability to do this depends on many factors, including effectiveness, stamina, health, and strategy.

A starting pitcher in professional baseball usually rests three, four, or five days after pitching a game before pitching another. Therefore, most professional baseball teams have four, five or six starting pitchers on their rosters. These pitchers, and the sequence in which they pitch, is known as the rotation. In modern baseball, a five-man rotation is most common.

In contrast, a pitcher who enters the game after the first pitch of the game is a relief pitcher. Occasionally, an opening pitcher is used for only a few innings, and is replaced by a long reliever or a pitcher who would typically be a starting pitcher.