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Alek Thomas

His path forward.

Alek Thomas
Alek Thomas
Photo by Thearon W. Henderson/Getty Images

With so much exciting success for the Diamondbacks, one player has not received the attention he merits. Last week, a friend gave me an Alex Thomas baseball card. He grabbed my attention. Thus started this article.

What is the path forward concerning the Diamondbacks’ glut of left-handed outfielders?

The Diamondbacks need their right-handed batting outfielders, such as Lourdes Gurriel Jr. and Kyle Lewis. On the other hand, they have five left-handed outfielders with exceptional skills. Which ones will be chosen as the future outfielders of the Diamondbacks? Age shows the path forward. Notice the two groups – age 23 and age 26.

  • 22.8 years Corbin Carroll
  • 23.1 years Alek Thomas
  • 25.9 years Jake McCarthy
  • 25.8 years Dominic Calzone
  • 25.8 years Dominic Fletcher

The two youngest (Carroll and Thomas) have the most potential for improvement. Carroll’s speed and batting skill are making him the NL leader for Rookie of the Year. Thomas’ defense in center field is the best of the current Diamondbacks, but his batting has rough edges that lowered him from a top-50 prospect in baseball. Nevertheless, this season several batting metrics improved suggesting he has not yet reached his ceiling.

How good is Thomas’ defense in center field?

Last season in center field, Alek Thomas earned 6 Defensive Runs Saved (DRS) and 7 Outs Above Average (OAA). That shows that he is by far the Diamonds’ best defender of center field. Before he was optioned to AAA, this season he earned 2 DRS and 0 OAA. (Data from The Fielding Bible and Baseball Savant.)

“…I’ve been out there since I’ve been 5, 6 years old [shagging balls in the outfield for the White Sox]…getting that big league feel about how guys hit the ball and how hard they hit it and the right reads and everything. That’s the biggest thing for me. My dad putting me in that situation….and watching video of great center fielders like Ken Griffey Jr.” — Alek Thomas.

Is there a weakness in Thomas’ batting?

“I think from a left-handed standpoint, we need that to become more consistent. We’ve identified some things in his swing that we feel like need to be adjusted slightly. It’s not taking away his personality or his individual swing mechanics. [It’s] trying to fine-tune those things to become more consistent.” — Tory Lovullo May 2023

“There’s a bit of excessive movement with the lower half which is creating some force moving forward. I know to impact the baseball but I feel like it was changing his sight lines.” — Torey Lovullo, May 2023

On 17 May, he was optioned to AAA with instructions to focus on improving his batting against left-handed pitchers. The following table shows his monthly wOBA against left-handed pitchers was in a general downtrend the last two seasons (starting at .242 and ending at zero).

Data from Baseball Savant.

On the other hand, his batting skills may have improved over the offseason but it did not show due to very few PAs. In 2023, April he had 29 plate appearances (PAs) and May he has 9 PAs.

How did Thomas improve his batting?

This season his wOBA declined (.277 to .255), while his expected wOBA improved (.277 to .304). The following statistics show that eventually his wOBA will likely improve:

  • Average exit velocity increased from 87.4 to 90.0 MPH.
  • Hard hits increased from 34.6% to 43.1%.
  • Barrels increased from 3.8% to 6.9%.

Alek Thomas improved his results against four seam fastballs (minus 2.2 to plus 1.7 RV/100) and against changeups (minus 3.8 to plus 1.1 RV/100) per Baseball Savant.

How can Thomas further improve his batting?

Crush sliders. Comparing this season to last season, his results against sliders got worse. The Run Value per 100 Pitches (RV/100) changed from plus 2.9 to minus 2.4 per Baseball Savant.

Former Diamondback Randy Johnson had an awesome slider. “He is particularly known for his overpowering fastball and devastating slider, a combination that remained effective throughout his lengthy career.” — Wikipedia

Let’s look at left-handed Diamondbacks batting against sliders from left-handed pitchers. The following table shows balls-in-play per swing, hits per swing, along with OBP, SLG, and wOBA. Three batters including Alek Thomas did not hit any sliders from left-handed pitchers. Ranking those three hit-less batters by balls-in-play per slider ranks them Pavin Smith, Alek Thomas, and Josh Rojas. So Alek Thomas is not the worst, but still has room for improvement.

Games through 6 June. Data from Baseball Savant.

Therefore, while in AAA Alek Thomas could practice batting against sliders to transform more of his balls-in-play into hits.

Since being optioned to AAA, let’s look at batting.

Data from

This season in AAA, his batting was better against LHP (.385 OBP & .500 SLG) than RHP (.350 OBP & .455 SLG). Even better is that his last six games show a hitting streak, with two 3-hit games. Update - through 11 June he extended his hitting streak to nine games. Hopefully one of his focus areas is better batting against sliders from left-handed pitchers. Unfortunately, I didn’t find statistics for specific pitch types for his AAA PAs.

One question in my mind is how do left-handed pitchers in the Majors differ from left-handed pitchers in AAA. Obviously, those in the Majors are more skilled, but there could be other differences. That would be important to consider.

Less ground balls.

In November, Jack Sommers’ season review of Alex Thomas pointed out that his 2.6% average launch angle was the second lowest in MLB, and that contributed to his 58% ground ball average, which was the second highest in MLB.

To be fair to Alek Thomas, his guidance in May of last season was to focus on getting hits instead of power hitting.

“I don’t want him to focus on getting hits and worrying about knocking the ball out of the ballpark. I want him to come in here, get into a routine, stay with his process.” — Torey Lovullo, May 2022

This season his ground ball rate improved from 58% to 54.0 in the Majors (55.2% in AAA), which was a step in the right direction.

On the other hand with the rules against extreme shifting, maybe his best path to success is with that high ground ball rate.

In December, Jack Sommers wrote about the possibility that Alek Thomas may be following the same developmental path as Adam Eaton, in which case Thomas will soon breakout with more success (albeit there are differences such as Thomas may have more power and Eaton may have more plate discipline).

Alek Thomas needs to develop his own best development path, even if his ground ball rate is higher than most successful batters.

Patience at the plate. This season Alek Thomas improved his patience at the plate. His pitches seen per PA increased from 3.60 to 3.93 (to about average in the Majors). His walks per PA increased from .054 to .065. Due to his increased patience, it is likely he is seeing more pitches that he wants.

This season while in AAA, when he improves his sight lines (see Lovullo’s comment), that will add to the effectiveness of his patience at the plate.

Although he may have been a tad too aggressive when he arrived in the Majors, his increased patience will lead to greater success.


Regarding the Diamondbacks’ glut of five talented left-handed batting outfielders, Corbin Carroll and Alek Thomas are favorites to be long-term Diamondbacks because they are the youngest.

Alek Thomas is a great defender in center field. This season his batting improved, mainly against fastballs and offspeed pitches. When he improves his results against sliders and his patience at the plate, his high ground-ball rate will not matter. Potentially he will be an All-Star starting outfielder.