Pitching places significant physical demands on the body, with physiological responses during a game showing
heart rate, oxygen consumption, and muscle enzyme changes indicative of moderate to high exercise intensity and potential muscle stress. A full game usually involves 120–170 pitches thrown by each team, and most pitchers begin to tire before they reach this point. As a result, the pitcher who starts a game often will not be the one who finishes it, and he may not be recovered enough to pitch again for a few days. The act of throwing a baseball at high speed is very unnatural to the body and somewhat damaging to human muscles; thus pitchers are very susceptible to injuries, soreness, and general pain. player
Noah Syndergaard pitching for the
New York Mets in 2015 Baseball teams use two strategies to address this problem: rotation and specialization. To accommodate playing nearly every day, a team will include a group of pitchers who start games and rotate between them, allowing each pitcher to rest for a few days between starts. A team's roster of starting pitchers are usually not even in terms of skill. Exceptional pitchers are highly sought after and in the professional ranks draw large salaries, thus teams can seldom stock each slot in the rotation with top-quality pitchers. The best starter in the team's rotation is called the
ace. He is usually followed in the rotation by 3 or 4 other starters before he would be due to pitch again. Barring injury or exceptional circumstances, the ace is usually the pitcher that starts on
Opening Day. Aces are also preferred to start crucial games late in the season and in the playoffs; sometimes they are asked to pitch on shorter rest if the team feels he would be more effective than the 4th or 5th starter. Typically, the further down in the rotation a starting pitcher is, the weaker he is compared with the others on the staff. The "5th starter" is seen as the cut-off between the starting staff and the
bullpen. A team may have a designated 5th starter, sometimes known as a
spot starter or that role may shift cycle to cycle between members of the bullpen or
Triple-A starters. Differences in rotation setup could also have tactical considerations as well, such as alternating right- or left-handed pitchers, in order to throw off the other team's hitting game-to-game in a series. and
Rafael Betancourt of the
Cleveland Indians warming up in the
bullpen Teams have additional pitchers reserved to replace that game's starting pitcher if he tires or proves ineffective. These players are called
relief pitchers,
relievers, or collectively the
bullpen. Once a starter begins to tire or is starting to give up hits and runs a call is made to the bullpen to have a reliever start to warm up. This involves the reliever starting to throw practice balls to a coach in the bullpen so as to be ready to come in and pitch whenever the manager wishes to pull the current pitcher. Having a reliever warm up does not always mean he will be used; the current pitcher may regain his composure and retire the side, or the manager may choose to go with another reliever if strategy dictates. Commonly, pitching changes will occur as a result of a
pinch hitter being used in the late innings of a game, especially if the pitcher is in the batting lineup due to not having the designated hitter. A reliever would then come out of the bullpen to pitch the next inning. When making a pitching change a manager will come out to the mound. He will then call in a pitcher by the tap of the arm which the next pitcher throws with. The manager or pitching coach may also come out to discuss strategy with the pitcher, but on his second trip to the mound with the same pitcher in the same inning, the pitcher has to come out. It is considered proper etiquette for the pitcher to wait on the mound until the manager arrives, whereby he then hands the manager the ball, and only then he is allowed to leave the field.
Relief pitchers often have even more specialized roles, and the particular reliever used depends on the situation. Many teams designate one pitcher as the
closer, a relief pitcher specifically reserved to pitch the final inning or innings of a game when his team has a narrow lead, in order to preserve the victory. More recently, teams began experimenting with an
opener, a relief pitcher who starts a game but only pitches at least the first inning. Other relief roles include
set-up men,
middle relievers,
left-handed specialists, and
long relievers. Generally, relievers pitch fewer innings and throw fewer pitches than starters, but they can usually pitch more frequently without the need for several days of rest between appearances. Relief pitchers are typically pitchers with "special stuff", meaning that they have very effective pitches or a very different style of delivery. This makes the batter see a very different way of pitching in attempt to get them out. One example is a sidearm or submarine pitcher.
Position players are
eligible to pitch in a game as well, this however is rare as these players are not truly trained as pitchers and risk injury. (For instance, in a 1993 game,
Jose Canseco suffered a season ending arm injury after pitching 2 innings.) Plus, they tend to throw with less velocity and skill. For these reasons, managers will typically only use a
position player as a pitcher in a blowout loss, or if they have run out of available pitchers in order to avoid a forfeit (the latter typically only happens in extra-inning games).
Cliff Pennington of the
Toronto Blue Jays, who pitched of an inning in game 4 of the
2015 American League Championship Series en route to a 14–2 loss, was the only documented position player to pitch during the
postseason, until
Austin Romine of the
New York Yankees pitched the ninth inning of Game 3 in a 16–1 loss against the
Boston Red Sox in the
2018 American League Division Series. The only regulation game in which
both pitchers of record were position players occurred on May 6, 2012, when the Baltimore Orioles' designated hitter Chris Davis was the winner in a 16-inning game against Boston while Red Sox outfielder Darnell McDonald took the loss. ==After the ball is pitched==