Who Fills the Strike Zone Without Balls in Play

Inspiration.

“We’ve got to start honing in on the pitching side of things, and we’re wanting to see guys commanding the baseball, commanding their secondary stuff, attacking the zone, filling up the zone.” — Torey Lovullo, 7 March

To the extent that Torey Lovullo’s comment reflects Diamondbacks’ pitching that is less than what it’s got to be, (and he is a straight-shooter), bullpen battles are incendiary. Spring training may add fuel to the fires. Let’s look at spring training data through 10 March.

Approach.

To increase comparability between pitchers, pitches are segregated into fastballs, breaking balls, and off-speed pitches.

To shed light on “filling the zone’ and ‘commanding the baseball’, let’s look at two things. First, what percentage of pitches are in the attack zone, and what percentage of pitches are in the combined attack zone / shadow zone per Baseball Savant? Second, what percentage of those pitches do not become balls in play? Instead, they are called strikes, whiffs, foul balls, and sometimes called balls (based on umpire judgement).

After this comparison, to add insights the pitchers will be also compared on more common (and all-inclusive for all pitch types) measures such as on-base percentage (OBP), slugging (SLG), wOBA, and hard hit percentage (HH%).

Compared two bullpen pitchers, who were acquired in the off-season.

The two pitchers were Jonathan Loaisiga and Kade Strowd. There are good reasons to be confident that Loaisiga will be on the opening day roster per this AZ Snake Pit article.

5 Bullpen Metrics. Kade Strowd’s hard hit percentage is one of the best in the Majors. In 2025 Strowd was better than Loaisiga in 4 of 5 metrics, per this AZ Snake Pit article.

For a second time, comparing those 5 metrics (in spring training through 10 March instead of last season), the picture is very different. The two pitchers were close to equal, with possibly Loaisiga having a slight edge. The following table shows the five metrics:

Filling the Zone. In spring training through 10 March, Loaisiga had higher percentages of fastballs and breaking balls that filled the zone. Also, Loaisiga when fastballs and breaking balls filled the zone, Loaisiga had less of those become balls in play. Details are in the following table.

4 Pitching Metrics. In addition, in spring training Loaisiga was better than Strowd in four more common metrics. For details see the following table.

Based on the comparisons, both pitchers are great with Loaisiga showing best in spring training.

Compared three left-handed bullpen pitchers.

Let’s look at Brandyn Garcia, Mitch Bratt, and Kohl Drake. Although the last two players were optioned to the minors on 8 March, the comparison may shed light on which pitcher is more likely to be called up if Garcia is injured or traded. Although Bratt and Drake might eventually be rotation pitchers, that doesn’t preclude them being called up to pitch in the bullpen.

Filling the Zone. Perhaps surprisingly, in spring training the three pitchers filled the zone close to the same percentages for both fastballs and breaking balls. Looking at whether those pitches became balls in play, there were differences. For fastballs, they were all great, but for in the attack zone they ranked Garcia (best), Drake, and Bratt. For in the combined attack zone and shadow zone, the rankings of Drake and Bratt switched. For breaking balls, Garcia and Bratt were great, with Drake at the bottom. Details are in the following table. It includes data from spring training through 10 March.

4 Pitching Metrics.

In spring training, Garcia had by far the best OBP, SLG, and wOBA. Bratt had the best HH%. So that may be a factor in why Garcia looks like he will be on the opening day roster.

Comparing Bratt and Drake, Bratt had the better SLG and HH%, while Drake had the better OBP. About equal was wOBA.

Details are in the following table. It includes data from spring training through 10 March.

Based on the comparisons, during the season it’s not clear to me whether I would call up Bratt or Drake. Maybe it would depend on which team the Diamondbacks were playing against, with one having the better matchups against opposing batters.

Looked at Philip Abner.

Despite being a left-handed He was not included in the 3-pitcher comparison. Last season, after an incredible rise from a+ to AA to AAA to MLB, he pitched 3.2 innings in the Majors with a 4.91 ERA.

Perhaps he has “big league stuff” and he would benefit from adding a “couple ticks” to his fastball velocity.

In spring training his average fastball velocity was 91.3 MPH. In spring training through 10 March, he filled the zone without allowing BIPs. “It’s possible the team could go with both [Garcia and Abner], if Torey Lovullo wants two lefties.”

Details are in the following tables. They include data from spring training through 10 March.

Summary.

Bullpen battles are incendiary, with filling the zone a factor.

Arguably, Jonathan Loaisiga and Kade Strowd will be in the opening day bullpen. Based on several comparisons, both pitchers are great with Loaisiga showing best in spring training.

Brandyn Garcia will likely be the left-handed pitcher in the bullpen on opening day.

If the team goes with two left-handed pitchers in the bullpen, Philip Abner could be in the bullpen on opening day.
Based on the comparisons, during the season it’s not clear which left-handed pitcher (Bratt or Drake) will be called up if needed.

Source link