Based on a conversation which originated at Beyond the Boxscore and continued over at The Book blog, FanGraphs created two new stats for relief pitchers based on WPA. Fortunately there are no intimidating acronyms. The positive one is "Shutdowns (SD)" and the negative one is "Meltdowns (MD)". I think everyone can understand that.
The Yankees are tied for the fewest meltdowns in the MLB with 8 but they've also had the second fewest appearances by relievers this year primarily due to the length their starting pitchers have provided for them. Yankee starters are averaging 6 1/3 IP per start and on nights when Javy Vazquez isn't pitching that number jumps over 6 2/3.
Looking at it another way, the Yankees' ratio of meltdowns to shutdowns is better than 1:2, which is good for 7th best in the league. Without getting my hands too dirty, that seems like a pretty good way to rank the performance of team's bullpens so far this season. When sorted by meltdowns/shutdowns, the teams fall out into three distinct tiers.
Tier 1: These teams all have a better than 2:1 shutdown to meltdown ratio. Most of them have an ERA better than league average with the exception of the Tigers (13th), Nationals (18th) and Pirates (dead last).
(The columns next to ERA and MD/SD are the
team's league-wide ranks in those categories)
What's apparently right away is that there is a decent general correlation to ERA but some extreme outliers (likely due to the fact that it's still early in the season).
The Tigers have a bullpen ERA that is slightly higher than league average but still have the best MD/SD in the MLB. Detroit has converted 80% of their saves (tied for 4th best in the league) which is a good indication that they have been getting the job done when it matters but giving up a lot of runs in low leverage situations. The Nationals are in the same boat with a bad ERA (19th), high SV% (11/13) and a solid MD/SD (5th). The Pirates are an interesting case, as their ERA is clearly inflated by having eight losses by seven runs or more, including two games they lost to the Brewers by a combined 33 runs. Those big losses have essentially no effect on WPA after a certain point but are given equal weight in ERA.
Tier 2: All of these teams have between a 1:2 and 3:4 MD/SD ratio.
The Reds have the fourth most relief appearances in the league so it makes sense that they have the most shutdowns with 33 and are in the top 5 for meltdowns with 18. They might have a good ratio but their ERA is indicative of the fact that their 'pen is over-taxed. Paging Aroldis Chapman. The Red Sox are in a similar situation with fewer shutdowns but a lower ERA. The Mariners are the only team in this cluster with an ERA in the top 1/3 of the league.
Tier 3: The final tier consists of teams who have more than 3 meltdowns for every four shutdowns. Four of them - the Cubs, Dodgers, Giants and Royals - have more MDs than SDs.
Incredibly, the Giants, who are leading the league in bullpen ERA, have only 10 shutdowns (last in the MLB) and are second to last in terms of their MD/SD ratio.
Clearly, over the course of the season, teams like the Giants and Tigers are going to see their ERA and MD/SD ranks converge on each other. The Giants will get some good performances from their relievers when it matters and the Tigers will see their guys give up some runs when it counts too.
Neither ERA nor MDs and SDs are perfect ways of measuring reliever's contributions but each brings their own unique perspective. And when combined with or contrasted against each other they have a way of teasing out information that we might not have known before. It should be interesting to keep on eye on these stats as the season goes forward and FanGraphs includes them on the player pages.