Reliever Sequencing, Real or Not?

I read this first article on reliever sequencing, and it seemed like a reasonable enough hypothesis, that batters would do better seeing pitches come from the same place and do worse seeing them come from somewhere else, but the article didn’t discuss the simplest variable that should have a big impact- does it screw batters up to face a lefty after a righty or does it really not matter much at all?  I don’t have their arm slot data, and I don’t know what their exact methodology was, so I just designed my own little study to measure the handedness switch impact.

Using PAs from 2015-18 where the batter is facing a different pitcher than the previous PA in this game (this excludes the first PA in the game for all batters, of course), I noted the handedness of the pitcher, the stance of the batter, and the standard wOBA result of the PA.  To determine the impact of the handedness switch, I compared pairs of data: (RHB vs RHP where the previous pitcher was a LHP) to (RHB vs RHP where the previous pitcher was a RHP), etc, which also controls for platoon effects without having to try to quantify them everywhere.  The raw data is

Table 1

Bats Throws Prev P wOBA N
L L L 0.302 16162
L L R 0.296 54160
L R R 0.329 137190
L R L 0.333 58959
R L L 0.339 19612
R L R 0.337 63733
R R R 0.315 191871
R R L 0.313 82190

which looks fairly minor, and the differences (following same hand – following opposite hand) come out to

Table 2

Bats Throws wOBA Diff SD Harmonic mean of N
L L 0.006 0.0045 24895
L R -0.0046 0.0025 82474
R L 0.002 0.0041 29994
R R 0.002 0.0021 115083
Total Total 0.000000752 252446

which is in the noise range in every bucket and overall no difference between same and opposite hand as the previous pitcher.  Just in case there was miraculously a player-quality effect exactly offsetting a real handedness effect, for each PA in the 8 groups in table 1, I calculated the overall (all 4 years) batter performance against the pitcher’s handedness and the pitcher’s overall performance against batters of that stance, then compared the quality of the group that followed same-handed pitching to the group that followed opposite-handed pitching.

As it turned out there was an effect… quality effects offset some of the observed differential in 3 of the buckets, and now the difference in every individual bucket is less than 1 SD away from 0.000 while the overall effect is still nonexistent.

Table 3

Bats Throws wOBA Diff Q diff Adj Diff SD Harmonic mean of N
L L 0.0057 0.0037 0.0020 0.0045 24895
L R -0.0046 -0.0038 -0.0008 0.0025 82474
R L 0.0018 -0.0022 0.0040 0.0041 29994
R R 0.0016 0.0033 -0.0017 0.0021 115083
Total Total 0 0.0004 -0.0004 252446

Q Diff means that LHP + LHB following a LHP were a combination of better batters/worse pitchers by 3.7 points of wOBA compared to LHP + LHB following a RHP, etc.  So of the observed 5.7 points of wOBA difference, 3.7 of it was expected from player quality and the 2 points left over is the adjusted difference.

I also looked at only the performance against the second pitcher the batter faced in the game using the first pitcher’s handedness, but in that case, following the same-handed pitcher actually LOWERED adjusted performance by 1.7 points of wOBA (third and subsequent pitcher faced was a 1 point benefit for samehandedness), but these are still nothing.  I just don’t see anything here.  If changing pitcher characteristics made a meaningful difference, it would almost have to show up in flipped handedness, and it just doesn’t.


There was one other obvious thing to check, velocity, and it does show the makings of a real (and potentially somewhat actionable) effect.  Bucketing pitchers into fast (average fastball velocity>94.5, slow <89.5, or medium and doing the same quality/handedness controls as above gave the following:

first reliever starter Quality-adjusted woba SD N
F F 0.319 0.0047 11545
F M 0.311 0.0019 65925
F S 0.306 0.0037 17898
M F 0.318 0.0033 23476
M M 0.321 0.0012 167328
M S 0.320 0.0022 50625
S F 0.321 0.0074 4558
S M 0.318 0.0025 39208
S S 0.330 0.0043 13262

Harder-throwing relievers do better, which isn’t a surprise, but it looks like there’s extra advantage when the starter was especially soft-tossing, and at the other end, slow-throwing relievers are max punished immediately following soft-tossing starters.  This deserves a more in-depth look with more granular tools than aggregate PA wOBA, but two independent groups both showing a >1SD effect in the hypothesized direction is.. something, at least, and an effect size on the order of .2-.3 RA/9 isn’t useless if it holds up.  I’m intrigued again.

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