How one of Clayton Kershaw’s most devastating pitches was born at Wrigley Field

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CHICAGO — Welcome back to Wrigley Field, the place where Clayton Kershaw's slider was born.

That's right, Kershaw first tried throwing the pitch on the side at Wrigley in late May 2009. Mike Borzello, the Dodgers' bullpen catcher who urged him to throw it and first caught it, is now — ahem – the Cubs' catching coach.


Borzello helped hatch baseball's Frankenstein monster, and now his Cubs must deal with Kershaw's slider and the rest of his arsenal when they face the ace left-hander on Sunday night in Game 2 of the National League Championship Series.

On Friday, the day before the series began, Borzello stood near the batting cage at Wrigley and pointed to the right-field corner. It was there that Kershaw finally relented in '09, telling Borzello that he wanted to try a new pitch.

Kershaw was just 21 in '09, a developing pitcher in his first full season. His ERA after 10 starts was 4.34, and he was averaging more than five walks per nine innings, preventing him from pitching deep into games. His repertoire consisted of two pitches — a four-seam fastball and curveball.

“When he was struggling, he kept asking, 'What do you got?'” Borzello recalled. “I said, 'You can't throw your curveball for strikes consistently. You're the most predictable pitcher in baseball. You throw a fastball every time in a fastball count. That's why your pitch counts are so high, why you're going five innings. You've got to come up with something else, a slider or something, and throw it for a strike.'”

Borzello said that after a month of such conversations, Kershaw approached him at Wrigley and said that he wanted to throw some sliders on flat ground.

“The first one he throws, I'm like, 'Oh my God,'” Borzello said. “I throw it back. He says, 'What do you got?' I say, 'Do that again.' He throws a few more and after he's done he asks me, 'What do you think?' I said, 'I think it's ready for your next start.' Kersh said, 'Are you kidding me?'

“I told him, 'It looks like your heater, but with depth at the end, a straight-down slider.”

“You like the pitch?” Kershaw asked.

“Yeah, I like it,” Borzello replied. “It's game-ready right now.”

Enter A.J. Ellis, who would go on to become Kershaw's close friend and favored catcher.

Normally, Borzello caught Kershaw's bullpen sessions, but the Dodgers had just recalled Ellis, wanting a third catcher for their series against the Cubs.

Kershaw was throwing the next day. Borzello, seeking a second opinion on the new pitch, asked Ellis to catch him.

“What do you got?” Ellis asked.

“Slider,” Borzello replied. “Wait until you see it. That's all I'm going to say.”

Here's Ellis' memory of the session:

“Kersh goes through his progression. He starts with his warmup, goes through his fastballs, curveballs and his changeups. Kersh doesn't know that I know. He kind of looks at me and says, 'Hey, I'm going to try a little slider here. Tell me what you think.'

“He gives me the slider sign. And I play dumb. I get on the inside of the plate. He throws the first one and it's like, the perfect slider, the perfect shape, the perfect speed, right underneath where a right-handed hitter's hands would be, back-foot slider.

“Borzi is right there next to me, about three feet away, just off the side of the bullpen mound on the first-base line. Him and I just kind of look at each other, this big wide-eyed look. Our mouths were open. He throws a couple of more, then Kersh finishes his bullpen, walks down, says, 'That slider, what do you got? Is it any good?'

“Borzi and I looked at each other again. 'Any good? That pitch is game-ready right now. That pitch is amazing. You need to throw that.' He goes, 'Ah, you think? Really?' I said, 'Kersh, take that into your next game.'”

As Borzello recalls, Kershaw thought both men were over-reacting, saying, “You guys are crazy.”

Kershaw said he didn't remember details of the conversation, just that Borzello and Ellis encouraged him to start throwing the slider in games.

He did, and the results were immediate.

Kershaw, in his final 20 starts of '09, produced a 2.03 ERA. The slider became his primary breaking pitch, and has been ever since.

Initially, Kershaw said, the pitch was more of a slurve. He throws it harder now, but says, “I have no idea why. It wasn't on purpose. It just kind of happened.”

He does recall Borzello urging him to come up with another pitch.

“Everybody was,” Kershaw said. “I had to get one. My curveball, I could get people out with it but it's not like a behind-in-the-count, flip-in-there-for-a-strike pitch. I've been working on the same changeup for 10 years and it hasn't gotten any better.

“I figured I'd better figure out something when (the count) is 2-1 and I've got the game on the line. Now I feel good throwing it to either side of the plate. It's just a different look.”

A different look?

As Borzello put it, “I didn't know it was going to be maybe the most devastating pitch of the next eight years.”

Since 2009, Kershaw has held opponents to a .156 batting average, .189 on-base percentage and .433 OPS with his slider — all major-league bests among pitchers with a minimum of 100 starts and 500 plate appearances ending on the pitch, according to STATS LLC.

On Sunday night, he will return to the place where the pitch was born, with Borzello, his former ally turned frenemy, in the opposing dugout.

Borzello smiled, then offered a mock lament.

“I wish I had never brought up the fact that we needed something else for a strike, dammit,” he said.