A.J. Burnett's career-saving sinker

The New York Yankees basically paid the Pittsburgh Pirates to take on A.J. Burnett after three awful seasons in the Bronx. Then came Burnett's sinker, and the rest was history.

Let’s get this out of the way first: We don’t know what’s up with A.J. Burnett, other than the fact that he’s mulling over retirement. A lot of unknowns still need to be pieced together, I know, but should Burnett opt to prolong his career for just a bit longer, he would stand to make a pretty penny in free agency, fresh off his best season as a pro--at the age of 36. That is, depending on which metric you prefer.

Wins Above Replacement (Burnett had a 4.0 fWAR in 2013) says he’s had a few better seasons in the past--three, to be exact. FIP, FIP- and a handful of others, meanwhile, paint a partially different picture.

On a FIP-level, only 11 other 36-year-old starting pitchers have ever mustered a lower FIP than the 2.80 mark Burnett had in 2013 (190 innings minimum). Only five have ever posted a lower FIP-. Finally, only one other starter has ever struck out batters at a higher clip. I could drop an "but wait, there’s more" line on you, but the point is already clear enough: Burnett’s 2013 season winds up in some darn good territory.

Trying to pin down just a single reason for Burnett’s resurgence is difficult because it’s a mixture of a handful of factors. But we’ll focus on one of the bigger themes, and that’s his increased usage of the sinker since joining the Piratesvia trade in February 2012.

In a visual, with the numbers coming courtesy of Brooks Baseball...

Note: Brooks Baseball’s Pitch FX data only goes back to 2007

The layman’s terms translation: There were plenty of fastballs until 2012, and then the sinker surfaced as Burnett’s primary hard pitch. Then, more sinkers in 2013. This is an interesting trend, one that sparks up a few ideas.

First, it’s worth acknowledging that a sinker and a fastball can be very, very similar. They’re both in the "fastball group" and the velocity of the two pitches is often comparable. If that was the case, this whole article would be a useless exercise. But, naturally, I made sure it wasn’t, finding that Burnett’s sinker draws enough horizontal movement to make it an entirely different pitch from a normal four-seamer.

Secondly, it’s worth speculating about the idea that Burnett intentionally started to wield his sinker more because the Pirates use defensive shifts to hedge their chances of gobbling up ground balls. It’s conceivable. More than conceivable, in fact, since sinkers generally induce grounders. And wouldn't you know it, Burnett's GB% since 2012 has ballooned to 56.7% after maxing out in the high 40's in the previous four years.

Of course, in saying that, we’re basically implying that Burnett can flip the switch on and off in terms of creating grounders.That, on the other hand, is tough to believe. Burnett struggled during his tenure with the New York Yankees, especially with home runs. Just four starters from 2009-2011 served up more long balls per fly ball than Burnett, and the result of all the dingers was, predictably, underwhelming, as only five other starters mustered a worse FIP-.

So intuitively, it’d make sense to question why Burnett didn’t throw his sinker more. Doing so would’ve given him the opportunity to keep the ball on the ground, instead of in the air. At the very least, it would’ve been a change of pace, something new.

But it’s not that simple. Very few things are that simple. Sure, we can say "do this, do that," but the big obstacle was the fact that Burnett had a hard time commanding his sinker, mustering a Strike% of just 22.82% from 2007-2011. It had plenty of pop, yes. It had enough horizontal movement, sure. But you can’t throw what you can’t locate. It’s useless.

Then, something happened. Maybe it was a slightly different release point that boosted Burnett’s sinker Strike% up to 27.84%. Regardless, it helped him improve in one very, very important situation: The dreaded hitter’s count.

Dreaded, of course, because of the drastic split differentials: When batters were ahead in the count, the league average OPS for pitchers was a lofty .957 (in 2013). That’s why you constantly hear the phrase "pitchers need to get ahead in the count" during broadcasts, radio shows, and things of that sort. It’s not just some arbitrary saying, as the league average OPS drops to merely .504 when the pitcher had the edge.

For Burnett, getting behind has been somewhat frequent. Of the 801 plate appearances opposing hitters had against him, 241 of them came in hitters’ counts, coming out to about 30%. That’s a decently-sized chunk, but, predictably, it’s been much bigger: 32% in 2012, 37% in 2011, 38% in 2010 and 37.5% in 2009.

With those numbers, there’s a readily noticeable trend: When Burnett was good, he was ahead more. When he was bad, well, take a guess. From 2009-2011, he struggled, pitching to a 4.36 FIP. He was decent in 2012. And we’ve already examined his fantastic 2013 campaign. Pretty simple stuff.

But what’s the purpose of all of this? Because Burnett used (and still does, a little) to struggle considerably when down in the count. Then came the sinker, which, to over-exaggerate, saved the day.

(Opponents' OPS against Burnett when they were ahead in the count)

The numbers are interesting because Burnett doesn’t lack for swing-and-miss stuff. In 2013, he posted a SwSr% of 10.6%, good for 14th in baseball (among all pitchers, relievers included). He owns a career 10% SwSr%. And one of the many perks of swing-and-miss stuff is the ability to pitch behind in the count without having to give into a hitter’s liking--a fastball, usually.

The table above doesn’t paint that picture. You’ll notice a bleak six-year stretch in which opponents annually cracked the 1.000 OPS plateau, and said stretch rendered Burnett a lousy 4.25 FIP.

It wasn’t until 2012 where Burnett climbed under the 1.000 OPS mark, and if you want to pick hairs, the .936 mark does qualify as above average. By a smidge.

And now, a drumroll for his 2013 opponents’ OPS with the batter ahead: .863. If you whip out a calculator, you’ll arrive at a 73-point improvement in a one-year span. Which is pretty substantial, when you consider how many runs are prevented by keeping hitters at bay while down in the count over the course of a full season.

So, those numbers pose the inevitable question: How did Burnett do it? Well, let’s get back to the original refrain: More sinkers. Though this time, the usage is almost doubled with the batter ahead.

Note: Since PitchFX data only goes back to 2007 on Brooks Baseball, we don’t get the whole sampling, but a seven-year span will do just fine.

The cut-and-dry version of the table: Over the past two years, Burnett has doled his sinker almost half the time when the batter was ahead. The word "outliers" does indeed come to mind, given the sharp increase from 2011 to 2012 and the subsequent 48.5% in 2013.

Again, we’re seeing the uptick in Burnett’s sinker usage followed by the solid results. They work in tandem, right? There’s definitely a connection, I’ll say that. But let’s not push it too far, because not only is Burnett using his sinker much more frequently, he’s also completely avoiding the batter ahead situation by pouring in more first-pitch strikes (career-high 62.4 first-pitch strike percentage in 2013). That’s one way to go about fixing the problem; it’s probably one of the better ways, too.

Perhaps, just perhaps, we’re overvaluing A.J. Burnett’s sinker. As aforementioned, it’s not just his sinker doing all the work. It’s just another weapon, after all. Except it’s a weapon that has kinda-sorta turned his career around after the Yankees essentially paid the Pirates to take him off their hands.

. . .

All statistics courtesy of FanGraphs, Baseball-Reference and Brooks Baseball.

Jake Dal Porto is a writer at Beyond The Box Score and Golden Gate Sports. You can follow him on Twitter @TheJakeMan24.

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