Does Leaving Guys on Base Reduce Runs?

I remember one of the many complaints of the Pirates in the early 2000s was that they had a few guys who could get on base, but nobody to knock them in. Since you have to score runs to win this was, of course, a problem. And so when the post-game show flashed the box score, including that the Pirates had left ten more guys on tonight, everyone shook their heads.

The inclusion of that number seemed to indicate that stranded runners are an important aspect of the game. If nobody was left on base that meant they were scoring. But is this actually true?

I don’t have numbers from the MLB, but I do have them from the Prospect League, which is a college summer wooden bat league that stretches from Pennsylvania to Illinois. Players typically come from Division I and II schools. In 2013, teams met for 326 games, which gives us 652 team games to look at how many runners were left on base and how many runs they scored. I separated each game by the number of runs scored (teams were shut out in 60 games, they scored one run in 70 games, etc.) and found the average number of runners left on for each run total.

Conventional wisdom would tell us that we should have an inverse relationship. The more guys who come around to score means there are less left on base, which is why we are happier when we see two guys were left on than ten.

What the numbers show is the opposite. Teams who scored three or less runs left an average of 7.05 guys on, while a team that scored four or more runs were leaving over 8.49 guys on base per game. Teams who were shutout left the lowest average on at just 6.21 runners. Why there is a sudden dip at eight runs per game is anybody’s guess.

(Click graph to embiggen)

Our conventional thinking is almost as if each team has a finite number of base runners each night, and the job is then to knock them home. This is obviously not the case and overall the numbers seem to indicate that hitting throughout a lineup during a game will develop into a snowball effect. On the other side, if a pitching staff is on, not only are they going to allow fewer runs, they are going to allow fewer runners period. The specific number of runs you get comes down to the timing of the hits.

I am not saying that it should be a goal to leave more guys on base. It is likely the other way around; the teams who score runs are putting more guys on base and so they are stranded when the timely hit is not there, but at least they gave themselves a chance to hit with runners on base.

If we look at the totals for MLB teams in 2013, we find only a .13 correlation coefficient between the number of guys a team left on base and the average number of runs they scored during the game. Obviously there is not much of a relationship here. Our line does have a positive slope though, again showing that it was not the inverse relationship that we had thought.

MLB Left-On-Base

In short, there is no sense in worrying about leaving too many guys on base. If anything, more is actually better.