I recently set out on a quest to determine the best way to evaluate relief pitchers in order to find the most valuable relievers this season. That led down a number of different paths of research that all centered around two main ideas. The key to success in relief pitchers is their ability to pitch out of jams and to pitch in big situation, which in a sense go hand in hand. Since the introduction of the save as a stat teams have began using their best reliever only in the ninth inning when they have a lead of 3 runs or less. However, this is not always the most important part of the game and often times the most important innings are the 7th and 8th.
So in order to truly determine the best reliever a good place to start is looking at the importance of the innings that each pitcher has thrown. This is where leverage index comes in. The higher the LI the more important the inning. This is a combination of score, situation, and place in the order.
The other key to relievers’ success is their ability to work out of jams. Often times a relief pitcher is brought in to the game with runners in scoring position. This is why ERA is not a good indicator of the success a reliever because it does not factor in the inherited runners that scored on that reliever. This is where RE24 can be of extreme help. RE24 is a counting statistic that uses a run expectancy table to show how many runs better than average a pitcher is based solely on game situation. This means than a pitcher will be penalized for allowing an inherited runner to score. However, since this is a counting statistic by dividing it by innings pitched it can be turned into a rate statistic, which allows more equal comparison between pitchers.
Since RE24 does not factor in the importance of the situation in the context of the game combining it with LI is a good determination of the value of the individual relievers. So in an attempt to determine this year’s best reliever I used this simple formula:
Reliever Rating (RR)=(RE24/IP)*LI
According to this stat the better the pitcher the higher the number and the worse the lower the number. A rating close to 0 indicates an average pitcher as a RE24 of 0 means the pitcher performed exactly as expected in the given situations. The worst ratings are the negative numbers meaning that pitcher was below average.
Here are the top 10 relievers according to RR thus far in 2014.
This list includes several big-name closers and several setup men. Looking at the value of these pitchers using this formula shows how not all inning pitched are equal. This is not a valuation of the true talent of the pitchers but what it does is create an even way of looking at the importance of each pitcher to their team. Not surprisingly, there are several closers among the leaders as due to the late game innings they pitch and the fact that they typically pitch in close games their leverage indexes are high. Yet for pitchers like Darren O’Day his high ranking is due to his very high RE24 total. This is due to O’Day’s ability to strand runners so far this season (96% LOB%). For a comparison, since 2000, the best single season total belongs to Jonathon Papelbon in 2006 with a RR of .95.
This can also be used to look at the worst relievers thus far this season.
Many of these names are not surprising as players like Nathan, Frieri, and Johnson failed miserably in their different stints as closers thus far this season. Many of these pitchers have very low RE24’s which supports their low ranking but pitchers like Steve Cishek (15th worst) who have been slightly below average (-3.18 RE24) are punished for struggling in high-leverage situations (2.11 LI).
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