Keynan Middleton: An Under-the-Radar Free Agent to Keep Your Eye on
In a stacked free agent market, it's easy to overlook Middleton, but don't sleep on him.
Opening
An under-the-radar free agent that I could see being very productive in the 2025 season is Keynan Middleton. He is a natural supinator with the ability to produce an effective repertoire with a fastball, slider, and changeup mix. His fastball and changeup are both effective, but I would like to see an adjustment to his slider to really take his arsenal to the next level.
Sadly, Middleton missed the entirety of 2024 with a forearm flexor tendon injury and was unable to pitch. Due to this, the Cardinals declined their club option for the 2025 season and allowed Middleton to take his talents to the open market. I believe Middleton can still be very effective in 2025 and should draw lots of interest from teams in free agency.
Delivery Characteristics
Before getting into Middleton's arsenal, let's take a look at his delivery characteristics. As I said earlier, Middleton is a stock-slot supinator due to his low spin efficiency on his fastball (90.2%), as well as his expected movement profile on his changeup. Despite this, Middleton has the ability to effectively get behind the ball on his fastball, while also being able to produce an effective changeup due to SSW, which I'll get into later. Middleton has a consistent release height from a 5.9 vRel due to his 39-degree arm angle and above-average extension of 6.8’, which allows him to produce this effective arsenal.
4 Seam Fastball
To start off, Middleton throws a 4-seam fastball. Middleton is able to produce an effective shape on this pitch with 15.9 iVB and 8.3 iHB while being thrown at 95.5 MPH. In 2023, this pitch was extremely successful, producing a .122 AVG, .234 wOBA, and .251 xwOBA. What makes this pitch so effective is Middleton's ability to generate 2” of unexpected ride relative to his arm angle. As a result, this pitch was able to produce an elite 33.0% Whiff%.
To go along with this unexpected movement, Middleton was able to produce an effective VAA of -4.4. This low VAA allows for this pitch to have a relatively flat approach angle to the plate, which allows for this pitch to be extremely effective at the top of the zone. Middleton currently throws this pitch at the upper ⅓ of the zone 56.0% of the time, which could be increased slightly to further improve the effectiveness of this pitch. Due to this, I would like to see Middleton increase the usage of this pitch to around 35-40% of the time, with a slight decrease of his slider/changeup.
Changeup
The next pitch within Middleton's arsenal is his changeup. Middleton is able to produce a very effective movement profile on this pitch with 6.6 iVB and 14.1 iHB while being thrown at 87.7 MPH. This pitch was very effective for Middleton in 2023, being able to produce a .211 AVG, .289 wOBA, and .217 xAVG with exceptional swing and miss results as well with a 37.4% Whiff% and 43.8% O-Sw%.
What makes this pitch so effective is its ability to generate over 10” of vertical separation from his fastball, despite being a supinator. The reason he's able to generate so much separation is his ability to produce SSW on this pitch. In other words, it's almost like his changeup is wearing a “costume”, allowing it to move in unexpected ways. As you can see below, he is able to generate unexpected movement relative to what is expected, which allows this pitch to be extremely effective. Middleton leans on this pitch heavily, throwing it over 43% of the time, which I could see being pulled down slightly to 35%-40% for an increase in the usage of his fastball.
Slider
The final pitch within Middleton's arsenal is his slider. Unlike the rest of his arsenal, this pitch isn't the most effective. Middleton generates a relatively decent shape of 3.0 iVB and 3.4 iHB while throwing it at 85.8 MPH, which graded out at 98 Stuff+. Due to this, Middletons 2023 slider generated below-average results of .286 AVG, .354 wOBA, and .296 xwOBA. Despite this, Middletons slider was able to effectively produce swing and miss with a 36.2 Whiff% and 32.0 O-Sw%.
What I would like to see Middleton do with this pitch is to make a slight tweak to revert back to his 2022 slider shape. As you can see below, he was able to throw this slider shape of 2.7 iVB and 2.9 iHB while being thrown at 84.6 MPH. Although they had similar shapes, this version of his slutter-like slider graded out at an above-average 111 Stuff+. Due to this, he was able to produce exceptional results of .176 AVG, .208 wOBA, and .243 xwOBA, with even better swing and miss results of 40.0% Whiff% and 35.7 O-Sw%.
My suspicion is that the issue with his 2023 shape stemmed from his inability to effectively control the increased horizontal break. What makes me suspect this is his drastic decrease in zone% where in 2022 he was able to zone this pitch 46.2%, in 2023 it fell all the way to 33.7%. I believe that reverting back to his 2022 slider shape would allow for this pitch to not only be more effective but also allow for it to be a threat within the zone. Although I want Middleton to revert back to his 2022 slider shape, I believe he should decrease the usage to around 20-25% to allow for the increased usage of his fastball.
Adjustments for Walk Rate
A major drawback in Keynan Middleton's productivity is his drastic walk rate, where in 2023, Middleton had a BB% of 10.8%. I hit on how reverting back to his 2022 slider could allow for him to decrease this walk rate, but I believe that a catcher positioning change could allow for his fastball to do so as well.
In 2023, Middleton was only able to zone his fastball 43.6%, consequently leading to the increased BB%. When looking at Middleton's fastball locations, we see he has a large variance of glove-side and above-the-zone misses. To counteract this, I believe the catcher should set up more towards the middle third of the zone so that these “misses” could become effective pitches on the edge of the zone.
Conclusion
All in all, I believe Middleton is an extremely under-the-radar free agent in this stacked relief pitching market. He has the ability to be a productive arm that shouldn't be too expensive due to his recent injury history. I believe he can be extremely effective in 2025 if he increases the usage of his fastball, continues to throw his SSW changeup, and decreases BB% by reverting back to his 2022 slider shape and changing catcher positioning on his fastball.