Playoff ready: Which teams built the best bullpens?

Now that the dust from the non-waiver Trade Deadline has settled, let’s get right to a very important question. Which contender has now positioned itself to have October’s best bullpen?

It’s a big question, because it’s been clear for years now that relievers are more and more important to a team’s success, especially in the playoffs. We’ve seen just how much top relievers like Aroldis Chapman and Craig Kimbrel have commanded in trade; we’ve seen just how the 2014 and ’15 Royals managed to push their way to the World Series. If you want to see which teams have the best bullpens this year, well, you can go right to MLB.com’s stats page and do just that. 

But there’s an important distinction to be made here, because playoff bullpens don’t look a whole lot like regular-season bullpens. For example, when you look at what the Rangers’ overall bullpen numbers are, you see baseball’s third-highest ERA, and you think that it’s a huge weakness. Yet it’s easy to forget that the overall number includes things like Tom Wilhelmsen and Luke Jackson both putting up ERAs over 10, and that has no relevance any longer — Wilhelmsen isn’t even in the organization any longer, and neither is going to be throwing high-impact postseason innings for Texas.

Every team cycles through around 20 or so relievers a season, but thanks to the extra days built into the postseason schedule, playoff teams use only a fraction of that number. Last year, the Royals’ top four relievers (Wade Davis, Luke Hochevar, Kelvin Herrera and Ryan Madson) threw about 46 percent of Kansas City’s regular-season relief innings, but more than 68 percent of the Royals’ postseason innings (including most of the high-leverage ones).

So it’s not really about “who has the best bullpen?” so much as it is about “who has the best top of the bullpen?” And that’s where we can make things interesting. Who now looks the best?

Well, we wanted to know, so we looked. There are 14 teams who have at least a 20 percent chance of making the playoffs per our postseason projections, so that’s who we’ll call “contenders.” We then took the top four expected relievers on the depth chart; while you could certainly quibble with those choices, swapping No. 4 and No. 5 won’t make much of a difference in most cases. And we ranked them using a combination of rank in ERA — because preventing runs matters — and Win Probability Added (specifically, the difference between Shutdowns and Meltdowns), because we know all too well by now that plenty of very, very good relievers aren’t racking up saves. (Hi, Andrew Miller!)

This is almost guaranteed to make fanbases angry. Let’s jump right in.

1. ORIOLES — 1st in ERA, 2nd in Win Probability (Zach Britton, Darren O’Day, Mychal Givens, Brad Brach)

Is this a surprise? It shouldn’t be a surprise. Britton (twice), O’Day and Brach have all made All-Star teams in the past two seasons. Britton’s combination of whiffs and grounders is unmatched; O’Day’s fastball has been untouchable. Then there’s Givens, who has struck out 94 in 77 2/3 big league innings. 

2. RANGERS — 3rd in ERA, 1st in Win Probability (Sam Dyson, Jeremy Jeffress, Tony Barnette, Jake Diekman)

That’s right, the Rangers — and this doesn’t include Dario Alvarez or Matt Bush. (Or Keone Kela or Shawn Tolleson, who have both struggled to reclaim last year’s glory.) But this is a very different Texas bullpen from the one that began the season, as Dyson’s 95-mph sinker has allowed him to solidify the ninth, and Jeffress, of course, arrives from Milwaukee with Jonathan Lucroy to add more talent. Barnette came from Japan; Diekman in the Cole Hamels trade. This isn’t a bullpen with many notable names. It’s just one that throws hard and gets outs.

3. DODGERS — 2nd in ERA, 5th in Win Probability (Kenley Jansen, Joe Blanton, Pedro Baez, Adam Liberatore)

This probably is a surprise, though perhaps less so than it ought to be. Jansen has been one of baseball’s most elite …

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