Blue Jays: Will the Bullpen Continue to Excel?

The Blue Jays bullpen has performed well this season but the forecast for the balance of the 2018 season is not as positive as their performance to date has been.

This article is the second of a two-part series. Part One examined the need for the Blue Jays to add a long reliever. Part Two will project how the bullpen will perform as the rest of the 2018 season unfolds.

This article was written prior to the news release regarding Roberto Osuna’s arrest. The analysis does not account for the ramifications for the team due to Osuna’s legal issues.

Part Two – Will the bullpen continue to pitch well?

More from Jays Journal

• Blue Jays: Adam Cimber, the unlikely decision King
• Toronto Blue Jays: Has the Shift Killed Kevin Gausman’s 2022 Cy Young Hopes?
• Blue Jays: What Yusei Kikuchi’s latest stumble should mean
• Blue Jays: Alek Manoah on pace to succeed in possible postseason
• Blue Jays: Bradley Zimmer has carved himself a valuable role

I will use two measures to forecast the ERA of the Blue Jays bullpen over the rest of the 2018 season: Expected Fielding Independent Pitching (“xFIP”) and Expected Weighted On-Base Average (“xwOBA”).

FanGraphs has a very good introduction to xwOBA and I encourage you to read it.

Per the FanGraphs article, xwOBA is described as follows:

"“Expected wOBA, or xwOBA, is a newer metric, the product of Statcast data. xwOBA is calculated with run-value estimates derived from exit velocity and launch angle”."

I used xFIP because it has one of the highest correlations with future ERA. With respect to xwOBA, the correlation with future ERA is not as strong as xFIP, but it does show promise. Also, with more reporting of exit velocity and launch angle, I thought it would be interesting to see how it compares with xFIP vis-à-vis future ERA.

How will the Blue Jays bullpen perform during the balance of the 2018 season?

Highlights

• As of May 6, the Blue Jays bullpen has posted an ERA of 3.06, which is the best in the AL;
• The bullpen is forecast to generate an ERA that is between the top quartile and median ERA for AL bullpens; and
• With the exception of Aaron Loup, each member of the bullpen will post ERAs that are higher than what they produced prior to May 7.

First, the relevant data is shown below.

American League Bullpens

Source: 2018 season up to and including May 6th games. xwOBA data courtesy of Baseball Savant; all other data was sourced from FanGraphs.

Observations

• Looking forward, xwOBA indicates that the Blue Jays bullpen will generate an ERA that is somewhere between the top-quartile (lower ERA) break point and the median;
• In other words, not as good as the season to date but better than more than half of the AL teams; and
• xFIP predicts a somewhat bleaker future for the Blue Jays than xwOBA does. xFIP projects a higher than average ERA from this point forward but better than the bottom half of the AL teams.

How will the individual relievers perform after May 6?

Blue Jays Relievers as at May 6, 2018

Source: 2018 season up to and including May 6 games. xwOBA data courtesy of Baseball Savant; all other data was sourced from FanGraphs.

Observations

• From a xwOBA perspective, Osuna and Barnes are projected to have ERAs that are higher than the other members of the bullpen and worse than the AL average;
• Compared to the season to date, xFIP foreshadows a higher ERA post-May 6 for each of the relievers with the exception of Loup;
• xFIP projects that only Osuna, Tepera, and Axford will have better than average ERAs; and
• xwOBA and xFIP point to a higher ERA for Osuna but they differ as to how poor his ERA will be on a relative basis.

Next: Blue Jays place Diaz on the DL, recall Urena

The last word

The Blue Jays bullpen has excelled so far this season. However, there are signs that the relievers will not maintain their performance level as the 2018 season unfolds. The Blue Jays bullpen has the third most appearances despite having the sixth fewest innings pitched. The lack of a designated long reliever has contributed to the elevated number of outings. More concerning is that two metrics (xFIP and xwOBA) forecast a higher bullpen ERA going forward. If the performance of the bullpen declines, the starters will have to be better than they have been to date.