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Left on base is a widely used statistic, because it can be used to evaluate hitters, pitchers, and even entire teams. While the name sounds simple enough, what exactly does it mean and how is it used?
Left on base (LOB) refers to how many runners remain on the bases at the end of an at-bat or inning. Hitters want to leave as few runners on base as possible, while pitchers want to strand as many runners on the bases as they can.
For individual hitters, LOB describes how many runners remain on base after the hitter records an out. For pitchers and teams, LOB describes how many runners remain on base at the end of an inning.
In baseball, the batting team’s goal is to score runs. Therefore, they do not want to leave runners on base at the end of the inning, because when runners are left on base, it means those runners have not scored.
A pitcher’s primary job is to prevent the opposing team from scoring. Therefore, when a pitcher strands runners on base — meaning those runners do not score — the pitcher has successfully done their job.
How LOB Is Used To Evaluate Pitchers
LOB is more helpful when it comes to pitchers than hitters. More specifically, the statistic left on base percentage (LOB%) is an important tool for evaluating a pitcher’s success.
LOB% measures what percentage of baserunners a pitcher prevents from scoring. Pitchers want to prevent runs, and so pitchers want to have a high LOB%. However, a pitcher can still succeed without a high LOB% simply by preventing runners from getting on base in the first place.
While most pitchers tend to have a LOB% close to league average, this is not always the case. Pitchers who record more strikeouts are likely to have a higher-than-average LOB%, because batters can’t drive runs in when they strike out. Nearly all other types of outs can lead to runs scored, but not strikeouts.
If a pitcher has a higher-than-typical LOB% over a short period of time, there’s a good chance that pitcher has been getting lucky. But if a pitcher has a high LOB% over a long period of time, it means they are almost certainly a very talented pitcher.
How LOB Is Used To Evaluate Hitters
For an individual hitter, LOB refers to how many runners remained on base after the hitter recorded an out at the plate. A hitter’s LOB for a game is the total amount of runners left on base after every out they recorded that game.
While LOB appears in box scores on MLB.com, most other baseball websites have eschewed this metric for individual hitters. This is because LOB is not particularly useful for evaluating a hitter’s performance or talent level.
For example, if a hitter comes up to the plate with a runner on second base and grounds out, there is a good chance the runner on second will be able to move over to third. The hitter successfully moved the runner over to third base, which puts the runner in a better position to score, and yet the hitter is said to have left a runner on base.
If the next hitter comes up and hits another ground ball, the runner on third will likely score. Even though these two hypothetical hitters worked together to drive in the run and both of them hit the ball the exact same way, the first batter is said to have left a runner on base while the second batter is not.
Scoring runs is a team effort, and therefore LOB is not a very useful statistic when it comes to individual hitters. Ideally, a hitter will leave as few runners on base as possible, but there is no such thing as a “good” or “bad” LOB for a hitter.
How LOB Is Used To Evaluate Teams
For a team, LOB refers to how many runners they left on base at the end of an inning. A team’s LOB for a game is the total number of runners left on base at the end of each inning.
LOB is slightly more useful for evaluating a team’s offensive performance than an individual hitter’s. This is because driving in runners — and therefore not leaving runners on base — is a team effort.
If a team has a high LOB for a game, it means the team did not capitalize on many scoring opportunities. When runners get on base, the offensive team’s goal is to drive those runners in. If several runners are left on base, the team may not have achieved that goal.
However, having a high LOB does not necessarily mean the team in question had a bad game. The more hits a team gets in a game, the more likely they are to leave runners on base. And yet getting hits is good – a team needs to get hits in order to drive runners in.
In other words, a team can have a high LOB and still have driven in enough runs to win the game. Therefore, as is the case with individual hitters, there is no such thing as a “good” or “bad” LOB for a team.
How Many Runners Get Left On Base In A Baseball Game?
The number of runners left on base in a typical baseball game varies widely. That being said, most teams average between six to eight runners left on base per game.
Ultimately, however, LOB doesn’t provide very much information about the game itself. If a batting team leaves a high number of runners on base, it could be a sign they did not drive in very many runs, or it could mean the very opposite — perhaps they got so many hits that they drove in several runs and still left runners on base.
Who Has The Best LOB% In MLB History?
In Major League history, the pitchers with the highest LOB% have been relief pitchers. Specifically, some of the best closers in MLB history have had a very high LOB%. This makes sense, as these pitchers are known for being able to come into games in difficult spots and finish the inning without allowing any runs.
Among pitchers with a minimum of 1000 innings pitched, Hall of Fame closer Mariano Rivera has the highest career left on base percentage: 80.4%.
Among starting pitchers with a minimum of 2000 innings pitched, three-time Cy Young Award winner Clayton Kershaw has the highest career left on base percentage: 79%.
What Is Considered A Good LOB% In Baseball?
Currently, the league average LOB% is around 72%. A good LOB%, therefore, is between 75% and 80%, while a bad LOB% is anything lower than 65%.
If A Runner Is Tagged Out, Are They Still Considered To Be Left On Base?
Technically, a runner can be considered left on base even if that runner is not literally left standing on a base at the end of an inning or at-bat. For example, if a runner is tagged out or forced out as part of a fielder’s choice or double play, that runner is still said to be left on base.
While the runner is not literally left on base, they are still a baserunner who did not score. The ultimate purpose of LOB is to measure runners who reached base and then did not score a run, and therefore it does not matter that the runner in question is not literally left on base.
What Is The Formula To Calculate LOB%?
Instead of just adding up the LOB totals you might see in a box score on MLB.com, the formula for LOB% – as calculated by FanGraphs – is as follows: LOB% = (H + B B + HBP – R)/(H + BB + HBP – (1.4 x HR)).
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