Win–loss record (pitching)
In professional baseball, there are two types of decisions: a win (denoted "W") and a loss (denoted "L") . In each game, one pitcher on the winning team is awarded a win and one pitcher on the losing team is given a loss in their respective statistics. These pitchers are collectively known as the pitchers of record. Only one pitcher for each game receives each type of decision. In certain situations, another pitcher on the winning team who pitched in relief of the winning pitcher can be credited with a save, and holds can be awarded to relief pitchers on both sides, but these are never awarded to the same pitcher who receives the win.
The decisions are awarded by the official scorer of the game in accordance with the league's rules. The official scorer does not assign a winning or losing pitcher in some games which are forfeited, such as those that are tied at the time of forfeiture. If the game is tied (a rare event), no pitchers are awarded any decision. A pitcher's winning percentage is commonly expressed with three decimal places.
A won-loss record is expressed in various ways. For example, for a pitcher with five wins and two losses, the record can be spoken and written as "five and two" and "five wins and two losses", and also written as 5–2. Won-loss records and these notations are also used in some other sports, when referring to teams' over-all or paired records, such as American football, basketball (e.g., http://espn.go.com/mens-college-basketball/team/_/id/8/arkansas-razorbacks) and tennis.
Winning pitcher 
In Major League Baseball, the winning pitcher is defined as the pitcher who last pitched prior to the half-inning when the winning team took the lead for the last time.
There are two exceptions to this rule. The more common exception is that a starting pitcher must complete five innings to earn a win (four innings for a game that lasted five innings on defense). If the starting pitcher fails to meet the innings requirement, the official scorer awards the win to the relief pitcher who, in the official scorer's judgment, was the most effective.
The second exception applies only to a relief pitcher who makes a "brief appearance" and is himself later relieved. If, in the official scorer's judgment, the relief pitcher was "ineffective", the win is awarded to the succeeding relief pitcher who was most effective, in the official scorer's judgment.
In the Major League Baseball All-Star Game, every pitcher is considered a relief pitcher for the purposes of this rule. For example, starting pitcher Matt Cain was awarded the win in the 2012 All-Star Game despite throwing only two innings.
Losing pitcher 
The losing pitcher is the pitcher who allows the go-ahead run to reach base for a lead that the winning team never relinquishes. A pitcher can be credited with a loss if he allows a runner to reach base, and is then replaced by a relief pitcher who subsequently allows that base runner to score. The pitcher receives the loss, even if this or any other runs are not earned. If a pitcher allows a run which gives the opposing team the lead, his team comes back to lead or tie the game, and then the opposing team regains the lead against a subsequent pitcher, the earlier pitcher does not get the loss.
If a pitcher leaves the game with his team in the lead or with the score tied, but with the go-ahead run on base, and this runner subsequently scores the go-ahead run, the pitcher who allowed this runner to reach base is responsible for the loss. This is true, regardless of the manner in which this batter originally reached base, and how he subsequently scored. If the relief pitching successfully completes the half-inning without surrendering the go-ahead run, the departed pitcher cannot receive a loss.
For example, on April 13, 2007, Carlos Zambrano of the Chicago Cubs was facing the Cincinnati Reds in the top of the 5th inning. He was taken out of the game with the Cubs leading 5–4 and the bases loaded. The pitcher who replaced him, Will Ohman, proceeded to allow two of the runners on base to score, giving the Reds a 6–5 lead. Although Zambrano was not pitching at the time the runs were scored, he was charged with the loss, as the base runners who scored were his responsibility.
The pitchers who receive the win and the loss are known, collectively, as the pitchers of record. A pitcher who starts a game but leaves without earning either a win or a loss (that is, before either team gains or surrenders the ultimate lead) is said to have received a no decision, regardless of his individual performance. A pitcher's total wins and losses are commonly noted together; for instance, a pitching record of 12–10 indicates 12 wins and 10 losses.
In the early years of Major League Baseball before 1900 it was common for an exceptional pitcher to win 30 or more games in one season with Old Hoss Radbourn of the defunct Providence Grays holding the record with an astounding 59 wins in 1884. Since 1900, however, pitchers have made fewer and fewer starts and the standard has changed. Gradually, as hitting improved, better pitching was needed. This meant, among other things, throwing the ball much harder, and it became unrealistic to ask a pitcher to throw nearly as hard as he could for over 100 pitches a night without giving him several days to recover.
In the first third of the 20th century (especially after the Live Ball Era), winning 30 games became the rare mark of excellent achievement; this standard diminished to 25 games during the 1940s through 1980s (the only pitcher to win 30 or more games during that time was Denny McLain in 1968, in what was an anomalous pitching-dominated season).
Since 1990, this has changed even further, as winning 20 or more games in a single season is now achieved by only a handful of pitchers each season. For example, in 2004 only three of the more than five hundred major league pitchers did so. In 2006 and again in 2009, no pitcher in either league won 20 games. The last pitcher to win 25 games was Bob Welch back in 1990.
The New York Times wrote in 2011 that as advanced statistics have expanded, a pitcher's won-loss record has decreased in importance. For example, Félix Hernández won the Cy Young Award in 2010 in spite of a 13–12 record. Many times a win is substantially out of the pitcher's control; even a dominant pitcher cannot record a win if his team does not score any runs for him. For instance, in 2004, Milwaukee Brewers starting pitcher Ben Sheets had a losing record of 12–14, despite displaying an easy league-best 8:1 strikeout-to-walk ratio and was among baseball's Top 5 in ERA (2.70) and WHIP (0.98). In addition to its dependence on run support, wins for a starting pitcher are also dependent on bullpen support. A starting pitcher can pitch brilliantly, leaving the game with the lead, and then watch helplessly from the dugout as the bullpen blows the save and gives up the lead. That would entitle the starting pitcher to a no-decision instead of a win despite the strong performance, regardless of whether or not the team ends up winning. Starting pitchers on teams with a weak bullpen tend to have fewer wins because of this. Likewise, a pitcher can give a poor performance and give up many runs and leave the game earlier than desired, but still win because his team scored even more runs. Some often prefer the quality start statistic as an indication of how many times a starting pitcher gave his team a realistic chance to win.
See also 
- MLB Official Rule 10.17
- Play-by-Play for Reds–Cubs game
- Kepner, Tyler (May 25, 2011). "Hapless but Not Hopeless, Blue Jays’ Reyes Carries On". The New York Times. p. B11. Archived from the original on May 25, 2011.