TCN 2021 St. Louis Cardinals Prospect #5 – Zack Thompson

photo: Zack Thompson (Palm Beach Cardinals)

Zack Thompson

Position: LHP
Born: 10/28/1997 (23)
Height: 6’2”
Weight: 225
Hits / Throws: L/L
Acquired: 2019 Draft – 1st round (19th overall)
Rule 5 Eligible: 2022

Click on the above photo to be taken to his player page at The Cardinal Nation, with additional biography and history information.

Link to Thompson’s career stats

2021 individual rankings – Brian Walton #5, Matt Thompson #5

Prior top 50 rankings – 2020 #7

Matt Thompson’s scouting report

Physical Description: Pretty maxed out physically, not much room for growth to the frame here. Proven bat-missing arm in college, strong collegiate producer in elite conference. Strong athletic lower half. Checkered injury history.

Mechanics: Thompson pitches from a high 3/4 arm slot. Uses his lower half extremely well, good rotation and excellent extension. Gets toward home plate so well that he gets excellent extension, which gives him a lower than average release point. Pitches play from delivery and slot extremely well.

Fastball: Sits in the low 90s, bumps up to 96. Above-average command but modest spin rate. Gets good running action on the fastball. Has a bit of natural sink to it as well. Grade: 55

Curveball: Slow, high spin offering sits around 74-75 with spin rates over 3000 RPM. Primary put-away pitch against right-handers. Outstanding depth, some horizontal break as well. Plus pitch, with some characteristics of a potential plus-plus offering. Grade: 60

Slider: Used primarily against lefties. Comes in around 83 MPH. Lacks depth but makes up for it with good horizontal break. Almost cutter like, but slower. Commands the pitch well but lack of depth (drop) makes it a pitch right-handers are likely to hit fairly well. Grade: 45

Changeup: Pitch comes in at low-to-mid 80s. Disguises it well, good arm speed and resembles fastball until it drops off the table. Average command of the pitch, and used primarily against righties. Wish he would throw it a bit more. Grade: 50

Command and Control: Thompson is a strike thrower and a proven strikeout generator. Kept a weak Kentucky team in the game against tough SEC lineups while he was on the mound. Locates well, and when he misses it’s mostly glove side. Grade: 55 Command 50 Control

Conclusion: It all comes down to health for Thompson, and if he can stay on the mound he has the ingredients to become a number three starter or backend reliever. Has one plus pitch which could turn into an elite one if he finds more velocity on the curveball. The fastball and changeup are average or better and the slider plays above-average against lefties. Could be one of the best arms in the 2019 class, depending on health.

Future Value: 50
Role: Mid Rotation SP
Risk: Moderate

Brian Walton’s environmental impact report

2019 recap

In the spring of his junior year, Thompson was one of the best pitchers in the Southeastern Conference. The then-21-year-old was 6-1 with a 2.40 ERA for the Kentucky Wildcats, striking out an impressive 130 in 90 innings.

Zack Thompson (University of Kentucky)

Thompson made his professional debut with the Gulf Coast League Cardinals, where he struck out four batters over two scoreless appearances. He finished at a much more challenging and appropriate level. With High-A Palm Beach, Thompson posted a 4.05 ERA over 11 games in short relief. Overall, he fanned 23 batters in 15 1/3 innings pitched, or 13.5 K per nine!

Thompson’s 2019 numbers were solid, but not extraordinary, as he was treated very carefully. As a result, he has not broken into any national top 100 prospect lists to date. In fact, he still has to climb over several prospects in the Cardinals system.

For example, in their recently-published Cardinals prospect list for 2021, Baseball America has Thompson fifth in the system. Same at MLB Pipeline, and now, The Cardinal Nation, too!

Here, Thompson was initially no. 6 in our rankings heading into 2020. However, after the acquisition of fellow lefty Matthew Liberatore, and his insertion into the 2020 top prospect list at no. 3, Thompson was one of the players to drop down a spot as a result. He jumped up two spots for 2021.

2020 recap – Assignments

  • January instructional camp – yes
  • St. Louis’ spring training camp – yes (non-roster invitee)
  • St. Louis Summer Camp – yes
  • Springfield alternate camp – yes
  • St. Louis – no

As the organization’s first-rounder from 2019, Thompson’s participation in the January 2020 instructional camp in Jupiter, Florida was a given. As then-new Cardinal Liberatore was not acquired until January 9 – after camp had already begun – it was Thompson’s final opportunity to strut his stuff as the system’s top left-hander. In fact, Thompson was cited by Baseball America as having the top curveball in the system – before Liberatore arrived – and he regained the distinction a year later.

Zack Thompson (Brian Walton/The Cardinal Nation)

There was a long period of time during which the Cardinals followed a practice of requiring every draft pick from the year prior to participate in minor league camp during their first spring in the organization as part of their indoctrination. That rule is no more, with Thompson’s non-roster invitation to St. Louis’ spring camp serving as the latest evidence of the shift in approach.

In his first, albeit brief big-league spotlight, Thompson performed at a level even better than advertised with three perfect one-inning outings, including three strikeouts. He was given meaningful innings, with his final pitch of the spring a swinging strike three by Nationals star Trea Turner.

Thompson was still in St. Louis’ camp when it was closed on March 12 due to the threat posed by COVID-19. He returned as part of the club’s summer camp in St. Louis in July and spent the remainder of the summer in the Springfield alternate camp. As such, Thompson was one of just a handful of top prospects who were deemed worthy of a 60-man player pool spot.

The return was potentially significant – two months of structured development during a year in which most of the minor leaguers in the system had to remain home. However, Thompson did not have 100% participation in the summer camp

With no media allowed in the alternate camp, reports on the activities in Springfield were filtered by what the Cardinals would share. Well after the fact, in November, Mark Saxon of The Athletic reported that Cardinals president of baseball operations John Mozeliak told him that Thompson had been “held back by shoulder soreness in summer camp, though Mozeliak said he finished in good health.”

Earlier, general manager Michael Girsch had alluded to Thompson’s lower level of alternate camp workload without providing specifics.

“He (Thompson) went to summer camp and he went to zero to 100 pretty quick,” Girsch told the Post-Dispatch’s Rick Hummel, “so we kind of eased him back to get him in good shape before we started stretching him out. He was a little behind Liberatore as far as accumulating innings down there but he did well.”

As expected, director of player development Gary LaRocque saw positives.

“He got planned innings and faced a number of hitters, where he was able to work on certain things that we wanted him to work on,” LaRocque told “Zack clearly got his work in. He’s got a great upside, and I don’t think this stopped any of that. It helped him.”

For 99% of the Cardinals minor league population, I would let the summer shoulder soreness pass with no more than a passing mention, if at all. But Thompson has a history that cannot be ignored. In fact, his left shoulder is probably the only reason he is a Cardinal today.

Many observers felt that health concerns were behind  Thompson’s fall in the 2019 draft to the Cardinals at pick no. 19 despite him being either the best or second-best college pitcher on the board, depending on the scouting source. Instead, he was the fifth hurler chosen in the first round.

His injury history includes a sore shoulder that limited Thompson as a high school junior and an elbow ailment as a sophomore at Kentucky, which caused him to miss seven starts and led to subpar results.

However, it was not an overwhelming concern, as he rebounded for a strong Cape Cod League showing and with USA Baseball following his sophomore year and had the aforementioned excellent junior campaign just prior to the 2019 draft. Still, in his three seasons at Kentucky, Thompson totaled under 200 innings.

This was another example of a pattern of the Cardinals taking the best player available, one with the talent to have been picked higher but was not. Yet, there was and still is some associated risk.

Of course, the Cardinals have far more details on Thompson’s medicals than the sketchy information available to us and are going to remain on top of his health. But they are not going to go public with any specifics. So, we will continue to monitor the situation as we head into another uncertain season.

2021 outlook

An unanswered question to me is how far Thompson is behind Liberatore. Recently, Cardinals manager Mike Shildt singled out the latter for his work in the 2020 alternate camp and noted he has the talent to pitch in the majors today. Thompson was not showered with the same level of praise, but that is nothing against him necessarily. The bar has been set high.

Zack Thompson (Palm Beach Cardinals)

As already noted, the body of Thompson’s contribution to date as a professional consists of just 15 1/3 innings mostly at High-A in 2019 and whatever work he was able to get in down in Springfield in 2020. Over the last four years combined, he has logged just 212 innings in official games, not all of which can be attributed to his health, however.

Given the low level of recent action, coupled with his medical history, it is tough for me to project how many innings Thompson will throw in 2021. If all looks good in the spring, he should be on the short list to join the Double-A rotation to start the season. A strong eight to 10 outings in Springfield could even lead to a bump up to Memphis.

But will those external factors lead the Cardinals to take preventive actions, such as to shorten his outings or have him pitch less frequently, or even shut him down earlier than normal? (It should be noted that these same questions could be asked for any number of pitchers.)

Future outlook

I want to be crystal clear that the preceding points are totally speculation that may be completely over-cautious. But it does seem clear to me that Liberatore is on a faster track to St. Louis.

Still, if Thompson can perform well at Double-A and Triple-A in 2021, it would put him in a good place to contribute to St. Louis in 2022. For the vast majority of prospects, that would be an admirable progression, so it is unfair (for me and you) to use Liberatore as a definitive yardstick (yet, I acknowledge that is precisely what I did).

As Matt notes, Thompson has the offerings to become a solid no. 3. Anything short of a regular rotation berth for St. Louis by the end of 2022 or start of 2023 would be a disappointment.

MLB debut: 2022

Our 2021 Top 50 series continues

To see the entire list of top Cardinals prospects, grading scales and remaining article schedule, click here. This includes the Top 50 countdown and 12 in-depth, follow-up articles coming up at the rate of one article per day through the remainder of the year.

50 Days, 50 Nights, 50 St. Louis Cardinals Prospects for 2021

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