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Kevin Slowey: Marlins Pitch F/X scouting report

The Miami Marlins have gotten a huge boost from non-roster invitee Kevin Slowey, as he has dominated in the early going. How does this season so far compare to his best year in the majors/

Jason Arnold

Kevin Slowey has been excellent for the Miami Marlins to start the season, and while luck is playing a role in Slowey's strong early start, he is still in line to put up a fantastic year even if he starts regressing on his performance with men on base or his home runs allowed. Once upon a time, Slowey was never a "good pitcher" so much as he was an acceptable one, having played parts of five seasons for the Minnesota Twins prior to this. He ran into some problems in the middle of his career, but his best year came in 2008, when he threw 160 2/3 innings and put up a 3.99 ERA and 3.91 FIP.

This year, Slowey's numbers are significantly better, but that is mostly due to the low home run total that is sure to regress to his norms; Slowey is still giving up fly balls at his typical career pace. But in terms of strikeouts and walks, his numbers in 2013 are fairly similar to 2008.

Slowey, Season K% BB%
2013 19.5 4.0
2008 18.8 3.7

How has Slowey pitched to yield these similar results? That is what I wanted to look at in this Pitch F/X report, courtesy of data provided by MLB Gameday and compiled by Brooks Baseball and the player cards feature.

Pitch F/X: The Basics

Once again, the basics are shown here. Here are the basic stats of Slowey's pitches in 2008.

Pitch Count Freq Velo (mph) pfx HMov (in.) pfx VMov (in.) H. Rel (ft.) V. Rel (ft.)
Fourseam (FA) 791 32% 90.88 -5.21 10.46 -2.45 5.76
Sinker (SI) 808 33% 90.73 -8.50 8.37 -2.39 5.74
Cutter (FC) 384 16% 86.66 0.75 6.87 -2.39 5.79
Curveball (CU) 300 12% 74.96 5.94 -0.74 -2.27 5.86
Changeup (CH) 191 8% 83.45 -6.13 7.57 -2.48 5.71

And here is what they look like in 2013 thus far.

Pitch Count Freq Velo (mph) pfx HMov (in.) pfx VMov (in.) H. Rel (ft.) V. Rel (ft.)
Fourseam (FA) 204 44% 89.28 -3.92 11.41 -2.11 6.08
Sinker (SI) 106 23% 89.41 -7.84 9.25 -2.12 6.08
Cutter (FC) 2 0% 81.55 -1.42 7.40 -2.18 5.98
Slider (SL) 71 15% 79.51 3.65 2.16 -1.95 6.25
Curveball (CU) 36 8% 73.21 4.30 -1.33 -1.86 6.28
Changeup (CH) 44 10% 83.77 -5.21 10.66 -2.03 6.14

Slowey's fastballs (four- and two-seamers) has dipped in velocity by about 1.5 mph since his 2008 season, and it seems as if the pitch has also gotten flatter over the years based on its increased vertical movement (higher vertical movement means more "rise" on a pitch, while lower movement means more "sink"). His usage rate on the fastball remains the same, at 65 percent in 2008 and 67 percent this season. As of late, Slowey has replaced his old cutter with a slider, and the two pitches are completely different entities. The curve is more "slurve" than the traditional 12-to-6 hammer curve, while the changeup has also flattened out as of right now.

The above shows one dangerous thing about Slowey's game: his pitches, in terms of movement and velocity, seem to be getting worse.

Pitch F/X: Performance

Here are his 2008 performance metrics, minus the balls in play data.

Slowey, 2008 B/CS Swing% Whiff%
Four-Seam Fastball 1.2 49.7 21.6
Two-Seam Fastball 1.7 50.3 15.0
Cutter 2.6 56.8 20.2
Curveball 1.8 43.7 19.9
Changeup 6.0 48.7 19.4

And here is how they compare to the 2013 model thus far.

Slowey, 2013 B/CS Swing% Whiff%
Four-Seam Fastball 1.2 47.5 18.6
Two-Seam Fastball 1.0 50 7.6
Slider 2.4 47.9 23.5
Curveball -- 47.2 11.8
Changeup 2.8 31.8 14.3

It is not difficult to glean one very clear thing from this analysis: Slowey's pitches are getting fewer swings and misses despite almost everything else being the same. His control of the strike zone remains impeccable, particularly with his fastball. The problem is that each pitch has been less effective, and it is not surprising since each pitch appeared less effective when we looked at the basic movement and velocity data. Slowey's fastball is most evident, as its whiff rate drops are fairly significant given how often he throws the pitches.

The slider may be the only change between now and 2008 that has been a positive difference. It looks strictly like a better pitch with more swings and misses and a similar balls to called strike ratio, and the two pitches were used in a similar capacity in 2008 and 2013 respectively. In general, sliders are just better pitchers versus same-handed hitters than cutters, which tend to have a smaller platoon split as compensation. Slowey was using both pitches primarily against righties, so this has been a good switch for him.


The other pitches have seemingly deteriorated from their 2008 high and now more closely match Slowey's career numbers if anything. In fact, his swinging strike rate of 7.0 percent this season exactly matches his career rate. Essentially, everything about Slowey's performance shows that regression should be on its way, from his loss in velocity to his decreasing effectiveness in whiffs. Unless he can continue the performance on balls in play, you should expect to see fewer strikeouts on the way for Slowey. Do no expect an uptick in walk rate, however, as his control has been maintained from then until now. Overall, he should be worse going forward than he was at the height of his abilities back in 2008.