How Good is Spencer Turnbull?

How Good is Spencer Turnbull?

Written By: John Moore
Follow Him on Twitter: @ajohnmoore
Follow Prospects Worldwide on Twitter: @ProspectsWorldW

Spencer Turnbull may have raised some eyebrows across the league with his very impressive start to this season. Turnbull is no stranger to good starts however as he had a 2.06 ERA through his first 8 starts last year before struggling with a 5.69 ERA over his final 21 starts of the year. Will Turnbull’s fast start to this year be another flash in the pan or has he made real adjustments that will allow him to continue this level of success?

To start, I’ll take a deeper dive into the numbers from last season. In Turnbull’s first 8 starts from last year he had 3.63 FIP and was striking out opponents at a 23.7% rate with a 9.5% walk rate. Over these first 8 starts he also had a SwStr% (Percentage of strikes that were swung at and missed) of 12%.

Looking at his numbers from the final 21 starts of last year he pitched in a total of 99.2 innings in these starts. As I previously mentioned, his ERA in the first 8 starts from last year was much lower than it was over his final 21 starts. His FIP over these final 21 starts however isn’t much higher than his FIP over the first 8 starts. By looking at the more advanced numbers I can see that he was pitching to much more contact overall over his final 21 starts. He started striking less batters out, walking less guys and getting less swings and misses. After watching Turnbull’s start against the Pirates this past Sunday (August 9th) I came away under the impression that his stuff and command both looked diminished from his previous couple outing this year.

Yes it is still a very small sample this year but Turnbull appears to be doing much better job this year at both missing bats and pitching to weak contact. His strike out rate has gone from 22.3% last year to 25.4% this year. Batters also appear to be making less quality contact overall against him as last year as the average exit velocity against him has decreased slightly from 89.6 MPH last year to 88 MPH this year. Barrels against him are also way done as the barrel rate against him has decreased from 6.7% last year to 2.2% this year. This is particularly surprising when you note that batters are chasing pitches out of the strike zone much less frequently against him than last year. Turnbull has been able to work more around the edges of the strike zone this year this is resulting in hitters making less hard contact against him overall. Knowing hitters aren’t hitting the ball as hard against him it isn’t too surprising to see his BABIP against much lower than last season, perhaps unsustainable.

Source: Baseball Savant


Turnbull is still relying on his four seam fastball at about the same frequency, 44%, as last year. His four seam fastball has added over 100 rpm’s of raw spin and is now ranks in the 80th percentile amongst fastball spin rates in the league. A fastball’s spin rate by itself however doesn’t necessarily mean a whole lot and there are times when less spin on a fastball is better. To judge the theoretical effectiveness of a fastball it might be better to look at spin rate but control for velocity. Bauer Units (RPM/MPH) allows us to do that.

Year Bauer Units
Turnbull Bauer Units by Year

Turnbull’s fastball velocity and fastball spin rate are both above league average, so it is no surprise that his Bauer Units are also above the league average mark of around 24. These above average Bauer Units means Turnbull will be most effective working middle/up in the zone with his fastball. Turnbull seems to be realizing this as he has been working up in the zone with his four seam more frequently this year.



YearSpin RateHorizontal Movement (inches)Vertical Break (inches)

Turnbull Fastball 9/29/2019

Turnbull Fastball 7/31/2020

His fastball has the makings of a very effective big league pitch. Like most four seam fastball’s however, the effectiveness of the pitch primarily relies on his ability to locate it. During Turnbull’s hot start to 2019 his fastball command was solid. This command wavered later in the season however and this certainly had a factor in his poor performance down the stretch as hitters started making much more consistent quality contact against it. Over the first 2 starts this year, Turnbull had good fastball command but in his 3rd start on Sunday August 9th his command appeared diminished from the previous 2 starts.

Turnbull’s overall numbers using the four seam this year have improved and he has been able to use the pitch to generate more swings and misses and weak contact than last year.


Turnbull has increased his sinker usage from 19.5% last year to 23.7% this year. While the pitch was crushed by opponent batters last season, Turnbull appears to have added some velocity this season and the overall effectiveness of the pitch has drastically improved. He is using it to generate more swings and misses this year and opponents are making less quality contact against it. Overall, opponents hit for a .420 wOBA against his sinker last year and while it is still a small sample, the wOBA against his sinker is down to .139 this year.

YearSpin RateHorizontal Movement (inches)Vertical Break (inches)

Turnbull Sinker 9/29/19

Turnbull Sinker 7/31/20

Despite the poor results using this pitch last year, Turnbull has increased his usage of it this year. The pitch is similar in movement to last year but, as previously mentioned, it has been almost a full MPH faster on average than last year. He appears to be working in the zone more with his sinker this year. Despite the early signs that this pitch may be improved over last season, I remain very skeptical of it and sinkers in this day and age in general really. To have success with this pitch Turnbull needs to be able to locate it and keep it out of the middle of the zone.


Turnbull is still using his slider at about the same rate he was last season. There have been some changes with his slider this year however, as the pitch is getting thrown about a MPH slower on average and it is getting about 100 more RPM’s of spin on average. This is resulting in the pitch getting 1.5 more inches of vertical break and about .9 inches more horizontal movement. This increase in movement is resulting in the pitch getting much more swings and misses and opponents haven’t been able to make as much quality contact against it. The whiff% on his slider has gone from 32.3% last year to 58.3% this year and the pitch also has one of the highest SwStr% rates amongst all sliders in the league. This has been huge for him early as he appears to have completely eliminated the other pitch, the curveball, he primarily used to rely on to get swings and misses in the past. Turnbull’s slider features a lower spin efficiency (around 30%) and this means it relies more on gyro spin to create vertical movement the pitch features.

YearSpin RateHorizontal Movement (inches)Vertical Break (inches)

Turnbull Slider 5/5/19

Turnbull Slider 7/31/20

The pitches new found ability to miss bats has meant Turnbull has been able to use it to put batters away using it at a much higher rate than last year. Turnbull has struggled to locate the slider at times in the past and will need to find a way to consistently be able to locate it if he wishes to continue having this level of success with it.


Turnbull has increased the change-up usage from less than 3% last year to 8.3% this year. This may simply be because the change-up plays better off the other pitches in his arsenal than his curveball. While the overall numbers look good so far in a limited sample, he is actually pitching to more and harder contact with it. The xwOBA against the change-up is .408, which is much higher than last year.

YearSpin RateHorizontal Movement (inches)Vertical Break (inches)

Turnbull Change-up 9/24/19

Turnbull Change-up 7/31/20

Despite the relative effectiveness of this pitch so far this year I remain very skeptical of it despite the fact that is has an increased spin rate and a 1.5 inch increase in average vertical drop this year. My skepticism is mostly because opposing batters have crushed it in the past and he isn’t able to get enough swings and misses using it.


As I previously mentioned, Turnbull appears to have almost completely abandoned the curveball this year. He has eliminated this pitch despite using it to get swings and misses at the same rate as his slider last year. Perhaps he has almost completely eliminated this pitch partially because he feels much more comfortable going to the slider to get swings and misses this year.

YearSpin RateHorizontal Movement (inches)Vertical Break (inches)

Turnbull Curveball 5/5/19


Turnbull has gotten off to a good start this year relying primarily on the four-seam, sinker and slider, which is pretty similar to last year. He has seemingly completely removed the curveball from his arsenal and replaced it by increasing the change-up usage. Turnbull has improved stuff overall compared to last year and Austin Romine’s game calling behind the plate appears to be having a huge effect on him. Overall, I remain very skeptical of Turnbull until he proves he can stay healthy which is definitely something he has struggled with in the past. He will also need to show the ability to more consistently command his pitches but he has appeared to have a more consistent release point early this year which will certainly help him in that department. Before other teams are willing to offer the Tigers much for Turnbull’s services, he will need to show the ability to deliver more consistently successful results.

Note: We are unsure of the accuracy of the new Hawkeye Tracking System or the potential differences between this and the previous Stat Cast system

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