Bullpens of the American League: Part 1 – the Setup

Welcome to part one of a four part series, covering bullpen performance around the American League this year. Hopefully by the time it wraps up, we’ll be able to see not only how well teams played this year but also how much the bullpen counts and what matters most in building a pennant-caliber bullpen.

The reason? Well, a lot of attention has been given and will be given to the Tigers offseason plans vis a vis second and third. More attention will be given to the fifth starter slot. But in spite of Valverde’s miraculous perfect season as a closer, it’s hard to argue that the rest of the bullpen wasn’t the Tigers biggest problem area, especially over the first four months of the season. In the playoffs, the depth and quality of the ‘pens the Tigers played against brought the message home to fans crystal clear.

The big ideas I’m looking to explore look something like this: how much more important is a top closer than your other key relievers? How much do your top two matter relative to the rest of the bullpen? How important is bullpen depth? And last: how important is luck or fortuitous circumstance relative to pure talent?

For the first two I’ll be looking at the top 7 relievers by appearances for each team in the American League, then separating out i.) the top save guy and ii.) the team’s top two by average game leverage index. Presumably the two guys you count on the most are the two guys that are entering the game in the most important situations. For iii.) I’ll be comparing those top 7 guys by appearances to the rest of the players who pitched for the team at some point during the year in terms of total contribution to the team’s W-L bottom line. For iv.) I’ll be comparing bullpens’ “pure” contributions in terms of WPA to what we would expect from the pitchers’ peripherals.

I can tell you in a nutshell what I expect to find: a tremendous difference between good and great in ace relievers, a disproportionately large contribution from the top two relievers for all decent bullpens, universally bad ‘other’ relievers with the critical factor being how many innings they pitch and an impact of luck seeming greater than that for any other role on a team.

But is that what I’ll find? Dunno. If you’re curious, check back tomorrow for a look at ‘number one’ for all 14 teams, including new $9 million man Papa Grande.