Analysis White Sox

White Sox: There’s No Reason To Be Bummed

One of the biggest bright spots for the White Sox in 2019 has been Aaron Bummer. Steve has more on him and what makes Bummer such an effective reliever.

Coming into the season, we all knew this was going to be yet another developmental season for our boys at 35th/Shields.  It was largely going to be about seeing what players would have Major League staying power and proving they can play an integral part in this process going forward.  We’ve seen some nice developments to this point in Lucas Giolito, Yoan Moncada, Tim Anderson, and even James McCann.  Every successful rebuild needs a few guys to come out of nowhere that aren’t on the prospect radar, even if those guys aren’t necessarily going to be huge contributors.

The game today is being dominated by Bullpenning, as analytical departments within teams understand the Time Through The Order Penalty (TTOP), having shut down relievers has become paramount to success for winning baseball teams.  There are signs that the Sox may have one of those weapons developing right in front of us.  While he won’t get a lot of fan fare, Aaron Bummer is the type of guy every championship caliber team needs in its bullpen if they hope to raise the Commissioner’s Trophy in late October/early November.

Bummer has pitched parts of three seasons with the Sox, and his statistical breakdown is interesting:

Season IP K/9 BB/9 ERA FIP xFIP
2017 22.0 6.95 6.14 4.50 6.16 5.25
2018 31.2 9.95 2.84 4.26 2.40 2.83
2019 17.1 8.31 2.08 0.52 2.16 2.83

I find it interesting that Bummer is very similar statistically to last season despite the drastically lower ERA.  Bummer is unique in today’s game that as a dominant reliever, he isn’t reliant on high strike out numbers to be successful.  What Bummer has done at an extremely high level this season, however, is get a ton of ground balls and weak contact.  When looking at his season breakdown, you notice a significant jump each season in terms of GB% and Average Launch Angle (in degrees):

Season GB% Avg Exit Velocity Average Launch Angle (in degrees) xSLG xwOBA
2017 54.4% 86.1 MPH 3.2 .362 .319
2018 61.2% 90.7 MPH 0.7 .380 .312
2019 72.5% 86.0 MPH -3.5 .201 .217

As you can see above, with each passing season, hitters are beating the ball into the ground more and more against Bummer.  In fact, among relief pitchers with at least 15 IP this season (SSS, I know), only Zack Britton has a higher GB% than Bummer’s 72.5%.  The negative launch angle and decline in Average Exit Velocity just simply illustrate that hitters have been unable to square up Bummer with any kind of success to this point.  The .217 xwOBA, which is an advanced metric you can find on that uses Statcast data, demonstrates the expected wOBA for a given batted ball dependent upon the launch angle and exit velocity.  That .217 number Bummer is currently displaying, is elite for lack of a better term.   Given where baseball is as an industry with regards to shifting and defensive analytics, this is a trend that if Bummer is able to continue will make him extremely valuable.

Pitch Mix and Effectiveness

Bummer primarily utilizes a three pitch mix with his Sinker, Cutter, and Slider.  Below you’ll see his utilization by season and the results against these three primary offerings:


Season % MPH Average Launch Angle (in degrees) Average Exit Velocity xwOBA
2017 44.9% 93.2 MPH -3.0 84.6 MPH 0.193
2018 55.7% 93.1 MPH -3.0 92.5 MPH 0.338
2019 69.1% 95.1 MPH -10.0 85.4 MPH 0.214


Season % MPH Average Launch Angle (in degrees) Average Exit Velocity xwOBA
2018 10.8% 89.0 MPH 0.0 81.4 MPH 0.214
2019 16.2% 90.0 MPH 16.0 86.7 MPH 0.226


Season % MPH Average Launch Angle (in degrees) Average Exit Velocity xwOBA
2017 36.9% 83.0 MPH 4.0 86.9 MPH 0.324
2018 19.2% 82.9 MPH 9.0 88.5 MPH 0.321
2019 12.4% 86.1 MPH 10.0 87.8 MPH 0.276

A couple of things really stand out from the above data.  First, we’ve seen a very significant uptick in velocity on Bummer’s Sinker and Slider.  He’s added almost a full 2 MPH on his Sinker with a full 3 MPH on the Slider.  The increased Slider velocity is probably playing a significant factor in the results when you look at the xwOBA against that particular pitch.  The increased Sinker velocity is likely playing a huge role in a hitter’s inability to square up the pitch, leading to the precipitous decline in launch angle against the pitch.  As such, Bummer is just overwhelming hitters with this weapon at the current moment in time.  Bummer added a Cutter to his repertoire in 2018 and to this point, it has been a very effective pitch for him that he has utilized to keep RHH at bay.  His increased Cutter usage has led to the overall decline in Slider utilization with each subsequent season.  This effective three pitch mix is something that will keep Bummer producing solid results in my estimation.  He’s mixing them up just enough to keep hitters off balance and ultimately keep the barrel off the ball.


Bummer has showed an ability to get out hitters from both sides of the plate this season.  Below you’ll see his season-by-season breakdown based upon handedness of hitters:

Against LHH

Season BA SLG Average Launch Angle (in degrees) Average Exit Velocity xwOBA
2017 .171 .341 5.0 85.8 MPH .321
2018 .245 .302 7.0 87.2 MPH .349
2019 .174 .217 -2.0 86.9 MPH .199

Against RHH

Season BA SLG Average Launch Angle (in degrees) Average Exit Velocity xwOBA
2017 .188 .406 1.0 86.4 MPH .326
2018 .338 .425 -3.0 92.8 MPH .289
2019 .059 .059 -5.0 85.0 MPH .225

For as dominant as Bummer has been against LHH in 2019, he’s been exponentially better against RHH.  Bummer is utilizing his Cutter 17.7% of the time against RHH and it appears he has developed a feel for the pitch as the results have been significantly better in 2019 than they were a season ago when the pitch was introduced.  RHH are slugging .167 against the Cutter so far this year, this coupled with his increased Sinker use has led to righties forcing the Sodfather to have to do some extra maintenance of the area around home plate thanks to Bummer.

The ability to get out hitters from both sides of the dish will be paramount for Bummer going forward.  Having a reliever come in that can bury hitters regardless of handedness gives Ricky Renteria or any future Sox manager a deadly weapon out of the bullpen.  This is the type of weapon that Terry Francona had during Cleveland’s recent run of success after they acquired Andrew Miller in 2016.  I’m not saying Bummer will be peak Andrew Miller by any means, but if he is able to keep up his performance at this level he will be a vital part of what is hopefully a future White Sox contender that can neutralize offenses during high stress October innings.

So all things considered, Aaron Bummer is proving to be a huge bright spot so far for our Sox in the 2019 season.  Relief pitchers are extremely volatile from season-to-season, so it will be interesting to see if the increased velocity Bummer is displaying to this point will lead to sustainable, long-term results.  If they do, the Sox have a weapon they can deploy in a variety of situations to shut down opposing offenses and help the Sox have a bullpen capable of being a serious threat should the team begin playing games of significance again soon.

Follow Steve on Twitter (@NWI_Steve) for more White Sox news and opinion.

Featured Photo Credit: Sean Williams/The Loop Sports


0 comments on “White Sox: There’s No Reason To Be Bummed

Leave a Reply

%d bloggers like this: