So Luke Hochevar has become a fairly decent pitcher in the second half, hasn’t he? Don’t believe me… Believe the splits:

Wow.

There’s a bunch that jumps out from that table. He’s shaved two whole runs off his ERA. He’s striking out three more batters per nine innings. He’s cut down on his base runners. And he’s done it all while walking the batters as roughly the same rate as before.

Hopefully, this was a strike. (Minda Haas/Flickr)

(WPA is Win Probability Added. It’s a cumulative number and is basically how many wins a player adds over the course of the season given his performance against “average” teams. Pitching God Roy Halladay is roughly worth 4.5 wins this season for the Phillies.)

Well done, Hochevar. Well done.

We know Hochevar. We’ve followed him since the Royals made him the number one overall (number one!) draft pick back in 2006. This run of quality outings is not only unprecedented, it’s entirely unexpected. He’s never, ever put together a string of starts like this. We saw it early in the season in a microcosmic fashion, when he could give five or six really strong innings… And then implode so spectacularly it rivaled one of those Sunday morning stadium demolitions (thinking Kingdome) for the fallout.

Now? The implosions (and the fallout) are seemingly in the past. A remnant of the first half.

The question then, is how has he done it? How has he pumped his strikeout rate and sliced his ERA?

The answer is simple. I’m going to boil it down to one word to you. Just one word. Are you ready?

Sliders.

Yes, it’s Hochevar’s slider that has become a weapon on par with weapons-grade plutonium. I will now refer to it as the Atomic Slider.

Before the All-Star break, Hochevar threw the slider roughly 11% of the time. According to PitchF/X, it was his fifth most used pitch. (PitchF/X is a little muddy on the types of pitches Hochevar throws. I suspect it’s a common issue with pitchers who throw a cut fastball and sinking fastball. According to their classifications, Hochevar throws a four-seam fastball, a cut fastball, a sinker, a curve, a slider and a change. I’m not worried about how to break down his fastballs and sinkers… The focus here is only on the slider.)

After the break, Hochevar has gone to the Atomic Slider over 18% of the time. It is now his second most used pitch.

It makes sense he’s leaning more heavily on his slider. According to data compiled by FanGraphs, it’s always been his best pitch. The raw numbers support this. Batters hit .163 this season when they put Hochevar’s slider in play. They are over .300 on all other pitches. It’s a pitch he should be throwing more frequently. He used to throw it a lot. He’s finally decided to return to his bread and butter.

OK… Hochevar is throwing more sliders since mid-July. So what? He was so horrible up to that point, just by throwing that one pitch more frequently can’t possibly explain his success. You’re skeptical. I don’t blame you.

Would you be surprised if I told you there was more to the slider than just an increase in times thrown? How about we discuss how Hochevar is throwing his best pitch.

From the excellent Texas Leaguers, here is a side by side comparison of Hochevar’s release point when throwing his slider. The chart on the left is his release point before the break. The chart on the right is his release after the break.

Notice, he’s lowered the arm slot on his slider, which may have something to do with it’s increased value. The new release point has allowed him to get a tighter spin on the pitch, so it has a greater horizontal break. Think of it as more of a sweeping motion, running away from right handed hitters. It’s also allowed him to add a full mph to the pitch. Before the break, his slider averaged 84.4 mph. Post break, he’s throwing the pitch at an average of 85.6 mph. It’s a small bump, but by bringing the velocity of his slider closer to the velocity of his sinking fastball, it allows Hochevar a little more deception in his arsenal. And as any pitcher will tell you, deception is the key in getting hitters out. In fact, where he is releasing his slider now… It’s almost exactly where he’s releasing his sinking fastball.

Compare the results Hochevar has experienced his slider from before and after the break…

Wow. Just wow.

Not only does he have the deception working for him, this slider is now a pitch he can really, really control. Almost three quarters are thrown for strikes… Are you kidding? And he’s getting a swing and a miss on almost a quarter of them? That just reinforces my theory… hitters see the low release point, quickly pick up the speed of the pitch… and think the ball is going to sink. Instead, it slides away (from right-handed batters.) All they can do is give up about halfway through their swing. And take their seat on the bench.

Again, look at the results. Here were Hochevar’s five most common plate appearance resolutions before the All-Star break:

Groundout – 25.3%
Single – 14.1%
Flyout – 13.9%
Strikeout – 11.8%
Walk – 7.3%

Compare those to his five most common resolutions post-break:

Groundout – 22.5%
Strikeout – 21.5%
Flyout – 14.2%
Single – 12.9%
Walk – 6.3%

The single and the strikeout have flip-flopped and the strikeout rate (as we previously discussed) experienced a crazy-huge increase. That’s why he’s been the best Royals starter in the second half. And it all goes back to his Atomic Slider.

We’ve seen crazy improvements from mediocre pitchers before. The question is always, “Can the improvement be sustained.” I was skeptical that Hochevar had really found true improvement. (In fact, I tweeted about him being another September tease, a la Kyle Davies in his second to last start.)

I think I was wrong about the whole “September tease” aspect. I think this improvement sticks.

Hochevar has changed his mechanics when throwing his best pitch and has made that pitch even better. It’s repeatable… It’s not the product of luck, or defense, or playing second division teams. This is something Hochevar should be able to do again and again. Because of that, we can reasonably expect him to give us something approximating his second half results in 2012.

On Thursday, the Royals announced they were shutting Hochevar down for the rest of the season. Not a bad idea for a couple of reasons. One, he’s thrown 198 innings, a career high by over 55 innings. And two, he’s had a great run of success. After going seven consecutive starts with over 100 pitches, he wasn’t as sharp his last time out against the Twins. There’s probably not much left in the tank. Don’t ruin a good second half because the guy is on fumes. It’s good to quit while he’s ahead.

Finally, does all this mean Hochevar morphed into the ace we’ve been missing all season? Not necessarily. But it does, in my mind, make him a solid number two or number three starter. And when Dayton Moore goes shopping for pitching this winter, that’s a very big deal. Think back to where we were at the start of the season… A bunch of number fours and fives. With Hochevar figuring out how to master his slider, the Royals have upgraded their rotation without having to explore the trade or free agent markets. Like I said, it’s a big deal.

Note: I noticed a couple of starts ago that Hochevar was having more success with his slider. That point was reinforced in a Tweet sent last week from Keith Blackburn (@doublestix) that caught my eye because we were thinking the same thing. There are several Royals fans out there with a keen eye and he’s one of them.