NEWSLETTER
After a brutal first week of the season in the bullpen, the Cubs have actually turned things around swiftly as guys have found their footing and roles have started to stabilize. While it’s true that the Cubs’ bullpen ERA is still dreadful overall (6.80, third worst in baseball), after the first week it’s been much closer to middle-of-the-pack (4.68, 12th worst).
Still, that’s not great. So how are the Cubs not, you know, blowing games left and right? Well, the answer is suggested up in that headline, and it’s because the bullpen’s Win Probability Added (WPA) has actually been 8th best in baseball (4th best in the NL).
As a reminder, WPA is all about how much your performance directly changed the likelihood of your team winning the game. From FanGraphs’ glossary:
Win Probability Added (WPA) captures the change in Win Expectancy from one plate appearance to the next and credits or debits the player based on how much their action increased their team’s odds of winning. Most sabermetric statistics are context neutral — they do not consider the situation of a particular event or how some plays are more crucial to a win than others. While wOBA rates all home runs as equal, we know intuitively that a home run in the third inning of a blowout is less important to that win than a home run in the bottom of the ninth inning of a close game. WPA captures this difference.
For example, say the Rays have a 45% chance of winning before Ben Zobrist comes to the plate. During his at-bat, Zobrist hits a home run, pushing the Rays’ win expectancy jumps to 75%. That difference in win expectancy (in decimal form, +.30) from the beginning of the play to the end is Ben Zobrist’s WPA for that play. The pitcher receivers a -0.30. If Zobrist strikes out during his next at bat and lowers his team’s win expectancy by 5%, his overall WPA for the game so far would be +.30 – .05 = +.25, as WPA is a cumulative statistic and is additive.
Basically I saw this tweet from FanGraphs, wasn’t TOTALLY shocked that the Cubs weren’t on there, but did wonder how close they were to missing the cut:
The five worst bullpens in MLB this season by WPA, in case you were wondering:
1. Astros (-2.65)
2. Phillies (-2.62)
3. Pirates (-2.58)
4. Angels (-1.89)
5. Reds (-1.64)https://t.co/vAnbx7izS4 https://t.co/w6vGU3gAuI— FanGraphs Baseball (@fangraphs) August 12, 2020
But, like I said, the Cubs’ bullpen has actually rated very well by WPA.
What that means, in effect, is that the Cubs’ bullpen has been terrible largely when it didn’t really matter. That makes sense when you consider the 11-3 record, right? When they had runs to spare, the Cubs bullpen gave ’em up. When the games were tight, the Cubs bullpen has actually pitched pretty darn well. Thus, by WPA, the Cubs bullpen has been great.
Does that translate to the Cubs bullpen having actually been great, or will continue to be great going forward? Eh. I mean, I tend to think there’s not necessarily a lot of predictive power in WPA, which is really more of a descriptive stat. That said, we’ve seen some indications in the past that when it comes to late-inning relievers – perhaps more than any other position or role – WPA can sometimes be a way of discerning relievers who can be at their best when the leverage is the highest.
Moreover, consider that some of the roughest performances in the bullpen have come from guys who have either been shuffled out already, or whose roles have been marginalized. As things stand right now – subject to rapid change, of course – I can think of several guys in the bullpen who I feel pretty good about: Jeremy Jeffress, Rowan Wick, Casey Sadler, Ryan Tepera, Colin Rea, and Dan Winkler. There are still plenty of questions about Duane Underwood, Jr., Craig Kimbrel, and Kyle Ryan, but that’s not a bad balance at the moment.
