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The Bullpen’s Very Bad Week

The bullpen has been a source of concern lately; what do the advanced stats say?

St. Louis Cardinals v San Francisco Giants Photo by Thearon W. Henderson/Getty Images

I’m sorry.

This is my fault.

Well, partially.

On April 17th, the San Francisco Giants were 7-2, and the future looked bright. I wrote a piece detailing how the starting pitching had led to massive success, their bullpen had underlying metrics that portended potential disaster.

I said: “Their bullpen has been much more pedestrian: although the Giants are fourth in the league in reliever ERA (2.15), their FIP ranks 16th (3.85) and their xFIP 25th (4.27). You know this: you’ve seen the last couple of torturous ninth innings that the Giants manage to squeak out of by the skin of their teeth. That doesn’t make the prediction systems all that confident, even if the results on the field look great. However, the Giants have capable relievers in their ‘pen; it’s just a matter of getting adjusted. The Giants are 27% worse than league average when it comes to reliever K/9 and 20% worse than league average for reliever BB/9: their relievers have had trouble striking out players as well as keeping them off the base paths.”

Now 26 games into the season, that same bullpen has become an iron anchor attached to the sinking ship that is the Giants, who have lost five straight and seven of their last eight. It’s not fair to blame all the problems on the bullpen—the offense has been reeling as well—but it’s time to see how the metrics have changed with regards to the bullpen.

Over the last week, there have been just three teams with a higher bullpen ERA than the Giants: the Red Sox (9.41), the Dbacks (7.91), the Reds (7.41), and then the Giants (6.75). Both the Dbacks and Reds are tanking; the Reds are tied for the worst 25-game start in major league history; the Red Sox are 10-17 and have a bullpen that seems destined to break its fans’ hearts. To have a bullpen on par with those three teams is to have one of the worst performing bullpens in the league. The Giants’ bullpen has allowed 21 runs over six games in just 28 innings.

The Giants ‘pen, though, isn’t as bad as it seems. Their season-long K/9 is 5% below average, and BB/9 is 9% below average. Below-average isn’t great, but those aren’t such drastic discrepancies as to make the ‘pen one of the worst in the league. And the advanced stats back this up: even in this miserable stretch with a 6.75 ERA, their FIP is 3.22 and their xFIP 3.67. Neither of those marks are the signs of a great bullpen, but it goes to show that they’ve been the victim of some very bad luck.

In that week-long stretch, the opponents’ BABIP has been .349 against Giants relievers, which is further evidence that they’re getting unlucky more often than not. Now, with a lower K/9, the BABIP does matter more since more balls are put into play. Their LOB percentage (percentage of runners left on base) is a dismal 53.2% (league average is usually around 70%), and that should also show potential for regression towards the mean.

They’re not this bad. But they’re also not that good, either. With a bullpen that ranks middle-of-the-pack, the offense has to be what steps up in the interim to give relievers buffer room to make mistakes. Over the last seven days, the Giants have hit exactly 2 home runs and have a wRC+ of 86; their team SLG is .287. That will not play when the pitching begins to struggle.

The takeaway here is that the bullpen is likely to begin to regress to the mean. They’re not going to be this bad for the full season. But they’re not going to be as good as they were in the beginning of the season when luck was breaking in their favor, either, and the offense will have to pick up the slack, or it’s going to be a long, tough season.