Caleb Thielbar's Secret Weapon (Exclusive)

If things had gone differently, Caleb Thielbar might have been in South Dakota, conducting recruiting visits and game-planning for a Division II baseball program as Augustana’s pitching coach. 

If he didn’t seek help from Driveline Baseball, he might not have added the necessary velocity or maximized each pitch’s effectiveness. If he did not get invited onto USA Baseball’s Premier 12 roster in 2019 – one composed of mostly young prospects – he might not have caught the attention of scouts with his high spin curveball and his now low 90s fastball. 

Instead, he’s reporting alongside the other pitchers and catchers in Fort Myers next month, returning to the Minnesota Twins as one of the most valuable weapons in the bullpen. 

Thielbar’s age-35 season was pretty impressive. He struck out 32.7% of hitters faced (20th best among pitchers who faced 200 or more batters). He allowed the lowest hard-hit ball percentages (25.9%) than anyone not named Lucas Luetge. 

What is unique about Thielbar is that as he ages, his velocity increases – the rare Benjamin Button effect for pitchers. 

When pitchers increase velocity, they discuss expanding the ceiling and the floor. Thielbar was capable of reaching 92.8 in 2020 but sat at 89.8. The following season, he was topping at 95.3 while sitting at 91.3. This past season, while the ceiling didn’t move much (he maxed at 95.5), his average fastball velocity was now at 92.8. 

Moreover, Thielbar’s secondary pitches also saw a good amount of velocity spike. In 2020, his curve averaged 68.7 but was up to 73.0 mph in 2022. The slider averaged 77.5 in 2020 and was now up to 81.3. 

Thielbar had a well-documented transformation at Driveline. Their pitching experts found minor issues with his mechanics overall. But they did find one area for him to attack in his remote training. Plyo drills, prescribed thanks to Driveline’s biomechanics analysis that revealed he had lower than usual hip-shoulder separation at foot plant, helped him improve this area of his mechanics and aided some of his velocity gains. 

He also acknowledged that he was trying to throw harder, as crazy as that sounds. When you compare the 2020 mechanics to this past year’s, you can visually see someone who indeed appears to be trying to throw harder. 

Still, Thielbar’s velocity improvement remained below average for major league left-handed relievers. Despite the gains, Thielbar’s fastball was at the 39th percentile for velocity in 2022. Nevertheless, at a 17.9% swinging strike rate, his fastball missed more bats than every reliever besides Pittsburgh’s David Bednar (who threw his at a slightly crisper 96.5 mph on average)*. 

So how was it so effective? 

Thielbar began to throw the fastball almost exclusively up in the strike zone. In 2021, when he threw fastballs in the upper half of the zone at a 57.6% rate, he had an 18.6% swinging strike rate (compared to a 5.2% one in the lower half of the zone). He went all in on upstairs in 2022 — 72.6% of fastballs thrown were in the upper half of the zone. 

Thielbar also said in July 2020 that he was trying to make his fastball spin as efficiently as possible. What Thielbar was trying to do was backspin the ball as close to north and south as possible. 

Thielbar achieved this by slightly altering his release to stay behind the ball more. According to Baseball Savant, in 2020, he owned an active spin rate percentage of 89% (100% being a perfect backspinning fastball). In 2021 that rate jumped to 91% and then 92% last season. Consider these pitch release charts below.

You need to know that the 0 line is north and south over the pitcher’s rubber. In 2020, his release was slightly over toward the first base side of the mound (13.9 inches), but he started to get that tighter back toward the center (6.4 inches in 2021). This past year that release point was nearly in line at 0 (4.1 inches). 

The average horizontal release point for left-handed pitchers is 25.0 inches. At 4.1 inches, Thielbar is a significant outlier. The only left-handed pitcher with a release point further to the right than Thielbar is his potential teammate, Danny Coulombe (who is at -4.3 inches and an extreme example in this category). The key is to give hitters different looks.

Why does this matter for Thielbar? Typically, the more a pitcher’s release goes away from the center, the higher probability that it will have a different axis that will impart side spin and detract from the optimal backspin he is seeking. By being behind the ball more, he reduces the amount of cut or run on a pitch and optimizes the carry. The fastball fell less this year than in his previous seasons—hence the ability to be so effective up in the zone. 

Essentially, Thielbar became more consistent and efficient in throwing his fastball. He could effectively locate the pitch in the upper third of the zone. The elevated fastball improves the quality of the secondary pitches that can tunnel out of that. 

Look at the performance of his breaking balls (slider and curveball) playing off an elevated fastball:

Caleb Thielbar | Breaking Balls Following Elevated Fastballs

By staying consistent with his fastball up in the zone, Thielbar would coax hitters to chase after his breaking stuff and, often, miss or make weak contact. 

Crafty is a word thrown around to describe what is often an aging left-handed pitcher who relies more on contorting the ball rather than blowing it past hitters. Thanks to technology and an advanced understanding of biomechanics, the lefty has not just prolonged his career but also thrived and dominated. In a different era, that might have been Thielbar’s destiny.

That said, it’s hard to say when the ride will end. Thielbar has pushed his velocity north each year, and it’s rare to see a pitcher continue to do so well into their thirties (after all, time is undefeated in reducing a pitcher’s radar readings).

In many ways, Thielbar is a crafty lefty. The word means being clever at achieving one’s aims. Through his acquisition of knowledge from Driveline and the Twins’ player development system, he has turned himself into a high-caliber relief arm.

Caleb Thielbar is one crafty mother. 

*Among relievers who threw 400 or more fastballs in 2022.