A Slippery Slider Slope

Note: special thanks to co-author Steve Sandmeyer aka Sandy

Welcome to game 5 as we as we continue our analysis of the World Series using Google Cloud. After an epic comeback in game 4, the Boston Red Sox have taken a commanding 3–1 series lead and are one win away from their fourth World Series Championship the last 14 years.

Boston will give the ball to left-hander David Price, who earned the victory in game two by going 6 innings, allowing just 3 hits, 2 earned runs and striking out 5. Price also appeared in relief in the 18-inning marathon in game three, throwing 13 pitches in ⅔ of an inning in which he allowed a hit and a walk but no runs.

Kershaw doing his thing

Los Angeles is hoping their own left-hander Clayton Kershaw will fare better than he did in game one, a start in which he didn’t make it out of the fifth inning and was ultimately charged with 5 earned runs in 4-plus innings. Many analysts feel it was because his slider was flat and too closely resembled his fastball for Boston’s hitters.

It (slider) was flat again against the Red Sox, and their disciplined hitters wisely laid off his curveball and noshed on his fastball in peppering him for seven hits over four-plus innings.

Even Kershaw himself acknowledged the issue:

“Definitely working on it,” he said of his slider. “Definitely trying to make it better. I focused on it. My bullpen focused on it, playing catch. I hope it’s better tomorrow.”

sl_stats  = pitches[pitches["pitch_type"]== "SL"]
            .groupby("game_date")
            .agg({ 'launch_speed':['mean', 'std']
                    , 'start_speed':['mean', 'std']
                    , 'break_angle':['mean', 'std']
                    , 'break_length':['mean', 'std']}).reset_index()

Simply put, if Kershaw can’t rediscover the movement and location of his slider, it could be a short outing for him, which could make for a long night for Dodger fans at Chavez Ravine. So what can the data tell about how the Red Sox fare against the slider in particular — and in which specific counts?

Let’s look at some data. For starters (no pun) — how flat was flat?

Note: If you want to get more into how we got here using Google Cloud — check out this post.

When looking at Kershaw’s appearances for 2018 you can see that velo, break angle and speed were down in WS game 1 AND he got hammered relative to launch speed (and also outcome).

The numbers are hard parse, but if we do a quick correlation test you see that there is moderate relationship between launch speed and break angle — so yes Kershaw was bit flat — his slider too closely resembled a fastball — and the Red Sox were able to take advantage of the situation.

How good are the Red Sox at hitting the slider? The second highest batting average and third highest slugging percentage — albeit on sliders not as fast and/or nasty as Kershaw’s on average IF (a big if) he’s back to his normal form. Safe to say if Kershaw regresses, the Red Sox will be ready to pounce

It seems just about everyone is feeling a bit flat after the grueling weekend of baseball and the rest of the real world happenings… let’s have a great game tonight and we hope to see the return of the Kershaw we all know and love — if for any reason to extend the series between two great teams.

NOTE: You can hack on similar data in BiqQuery by heading over to our public datasets hosted on Google Cloud. After the World Series we will post new data from 2018.