07 June 2014

Some More Looks at Suk-Min Yoon

When the Orioles signed Korean pitcher Suk-Min Yoon this past spring, no one was really sure what to expect. Would he be a starting pitcher, or a relief pitcher? Would he help the Orioles in 2014, or would there be a transition period? In spring training, it became obvious that he would have to spend some time in the minor leagues. He was optioned to Norfolk and has spent the entire season as a member of the Norfolk starting rotation.

On the surface, he hasn't pitched very well. He has a 2-5 record, with a 5.67 ERA and 69 hits allowed in 54 innings. He's allowed 9 home runs and has only struck out 35 batters in the 54 innings. He has shown good control, with only 11 walks allowed. However, these numbers are somewhat misleading in that he's had two really terrible starts:


IP
H
R
ER
BB
K
GS
April 8
2 1/3
11
9
9
1
0
-2
May 4
3
11
8
8
0
2
7

(The GS column is the Bill James Game Score.)

As it happened, I saw both of those games as the milb.com datacaster. I've also seen two of Yoon's other starts, one as the milb.com datacaster and the other as a Baseball Information Solutions scorer:


IP
H
R
ER
BB
K
GS
May 14
5 2/3
6
4
4
0
5
46
May 31
7
6
1
1
0
5
66

Everyone in the press box for both of his bad starts noticed that the opposing batters were generally hitting Yoon early in their at-bats; Yoon wasn't going deep into counts. I noticed in his May 31 start that the opponents - the Pawtucket Red Sox - were working deep counts and weren't very successful. I looked in more detail at the four starts I've seen to see if there's a pattern. The following table documents the number of at-bats resolved in each number of pitches, 1-8:

Pitches
In AB
1
2
3
4
5
6
7
8
April 8
1
6
4
4
0
1
1
0
May 4
2
7
4
6
1
1
0
0
May 14
3
4
2
6
3
4
1
1
May 31
5
3
6
3
4
3
2
0

Definitely, when Yoon didn't pitch well, opposing batters were not going deep into counts. And, in the games when Yoon did pitch well, the opposing batters worked more deep counts. The following table shows the OPS of the batters at each pitch total:

Pitches
In AB
1
2
3
4
5
6
7
8
April 8
.000
2.000
1.750
2.500
-
1.000
.000
-
May 4
1.500
2.571
1.000
1.700
2.000
.000
-
-
May 14
.000
.000
2.500
1.500
.667
.000
.000
2.000
May 31
1.000
1.000
1.000
.667
.000
.000
.000
-

We wouldn't expect to get a perfect correlation pattern with so few at-bats, but a pattern seems to be emerging. In general, working the count against Yoon wasn't a successful strategy. Hitting the first pitch wasn't generally successful - in the May 31 game, one of the five batters who put the first pitch into play hit a home run, so the slash stats were .200/.200/.800 - but putting the ball in play in pitches 2-4 was very successful.

Why would Yoon be so much more effective when batters are seeing more pitches? It's possible that Yoon wasn't throwing quality strikes early in the count, so that batters were teeing off on easily-hittable pitches. As he got deeper in the count, he felt more comfortable working near the edges of the strike zone. If this is the case, batters trying to work the count would be disadvantaged by not swinging at more-hittable pitches and being forced to swing at less-hittable pitches. Another possibility is that as he gains more American experience, he's not feeling the need to throw get-me-over pitches to get ahead in the count. Batters swinging early in the count are missing or fouling off more of them. If that's the case, batters trying to work the count might be advantaged by not swinging at pitches outside the strike zone.

The best batter strategic approach to facing Yoon is obviously different depending on whether Yoon is continuing to focus on getting ahead in the count or he's becoming more comfortable "nibbling" early in the at-bat. Also, we don't yet know if Yoon can consistently avoid terrible outings like those of April 8 and May 4. The Orioles probably shouldn't promote Yoon before the all-star break, and they may be best served by letting pitch the full season in the Norfolk rotation.

Addendum: A minor methodological point in case someone wants to check on or augment my figures. Any partial at-bats in which the third out of an inning was recorded on the base path (a caught stealing or pickoff) were excluded.

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