Francisco Liriano and the value of a great slider

If you’re like me, you might have watched the vast majority of the Pittsburgh Pirates’ series against the Colorado Rockies this past weekend. Being a Rockies fan is my unfortunate lot in life, so I have a lot of bad weekends.

Of course, if you’re a civilized human being who enjoys good baseball, you didn’t bother watching this series. But if, if you did, you were probably compelled to notice several things. First, the Rockies are profoundly bad at baseball right now. The second, and more pertinent to this particular piece, is that Francisco Liriano should probably be a much better pitcher than he has been this season.

We’re talking about a guy whose xFIP and SIERA (while mirroring each other) have varied almost as much year-to-year as they have game-to-game. But why? Liriano clearly has the stuff to be an elite major league pitcher. His 2013 season was impressive by any traditional measurements and even most peripheral ones, following up nice performances in 2006, 2008 and 2010. He’s been pretty pedestrian in 2014, however, which is more in line with 2009, 2011 and 2012 for the left-hander.

For starters, with the notable exception of last year, Liriano is a player who has spent the better part of six seasons underperforming to his SIERA. Observe:

YEAR	IP	SIERA	ERA
2005	23.2	2.15	5.70
2006	121.0	2.55	2.16
2008	76.0	4.22	3.91
2009	136.2	4.37	5.80
2010	191.2	3.01	3.62
2011	134.1	4.52	5.09
2012	156.2	4.19	5.34
2013	161.0	3.43	3.02
2014	81.1	3.88	4.43

In addition to the table, it’s noteworthy that for his career, Liriano is underperforming to his SIERA by about a half a run.

It’s not surprising that this estimator believes that Liriano should be a better pitcher this season. In fact, it’s a little eyebrow-raising that his SIERA isn’t even lower. The lefty has the eighth highest K/9 clip in the game among starters who have hurled at least 80 innings, to go along with an impressive 18.2-percent line drive rate and 52.7-percent ground ball rate that both rank Liriano in the top-20 among major league starters.

Unfortunately, for all of the areas where Liriano excels as a pitcher, there are just as many areas that could be described as disastrous. For example, no starter in baseball has a lower Zone% than Liriano’s 37.4-percent. Furthermore, even though Liriano trails only Clayton Kershaw and Masahiro Tanaka in all of baseball in swinging strike rate, he’s only inducing swings on pitches outside the strike zone at a very average 31.9-percent clip, while the two men ahead of him in swinging strikes are also tops in the league in O-Swing%.

This correlates to two other numbers of Liriano’s that have been particularly damning: His 4.98 BB/9 ranks as third-worst in baseball and his 14.1-percent HR/FB ratio is 12^th worst.

While limiting walks and home runs is obviously a big key for any pitcher, the correlation for Liriano is especially obvious. Here’s the same table as before, with BB/9 and HR/FB added for each year:

YEAR	IP	SIERA	ERA	BB/9	HR/FB
2005	23.2	2.15	5.70	2.66	26.70%
2006	121.0	2.55	2.16	2.38	13.20%
2008	76.0	4.22	3.91	3.79	7.70%
2009	136.2	4.37	5.80	4.28	12.50%
2010	191.2	3.01	3.62	2.72	6.30%
2011	134.1	4.52	5.09	5.02	9.90%
2012	156.2	4.19	5.34	5.01	12.90%
2013	161.0	3.43	3.02	3.52	8.30%
2014	81.1	3.88	4.43	4.98	14.10%

It comes as no surprise that Liriano’s four best seasons have coincided with a low BB/9, HR/FB, or both. But what’s been the difference for him in his most successful seasons versus his less successful ones?

In the past, some of this could be attributed to Liriano’s management of his fastball. Three of the four seasons in which he used his fastball the most (not pictured below - but rate of usage was highest in ’08, ’09, ’11 and ’12) are also the ones in which he struggled the most. And indeed, pitch values from FanGraphs label his fastball as a profoundly poor pitch in those seasons:

It wasn’t any better of a pitch in 2013, but Liriano did drop his use of his fastball by almost 10-percent last year, and it has remained down this year, but is weighted as an even worse pitch. Still, the distribution of Liriano’s arsenal should help to offset this effect at least somewhat, especially with his change-up getting better all of the time.

It’s probably obvious from the pitch values table, but I’d contend that the drop-off in the effectiveness of Liriano’s slider is the biggest culprit this season. It’s not that his slider is a bad pitch per-se, it’s that what was once his best pitch is now an extremely average one, and even marginally below average this season, yet he’s throwing it at an identical rate.

To wit, a pitch that was saving Liriano two runs per 100 sliders thrown last season (and 1.75 runs per 100 for his career) is now an average pitch for him.

In particular, Liriano has struggled throwing the pitch to lefties, with ten of them reaching base against it this season in 126 pitches. That’s in contrast to 2013, when he threw his slider to lefties 207 times with only eight reaching base against that pitch all season. Certainly, it helps to explain Liriano’s reverse platoon splits (.378 wOBA against lefties versus .309 against righties). He’s also had a 2-percent drop in his swinging strike rate with the slider and an almost 4-percent increase in sliders thrown for a ball against lefties.

On the other side of the plate, Liriano’s swinging strike rate with his slider against right-handed bats is almost identical to last season’s, but again he’s throwing it for a strike almost 3.5-percent less than last season.

Then there’s this:

The last two seasons that Liriano’s release point on his slider was around 6-feet or higher also happen to be the two full seasons (before 2014) that that pitch was least effective. Granted that it has never been this pedestrian in the past, but if his release point is not where Liriano is most effective, then it certainly accounts for some of the drop-off.

I’d be remiss if I didn't also point out that Liriano’s slider has dropped in velocity this season. The pitch that was so effective last year was a full two miles-per-hour faster than its current iteration. While that hasn’t been necessarily preventative of his success in the past (it’s been below 86 mph in four other seasons), a drop as precipitous as that would absolutely impact the effectiveness of the pitch.

Since returning from the disabled list, however, Liriano’s slider is back to averaging just over 86-mph. Against the Rockies he threw 25 of 34 sliders for strikes, including nine whiffs. Colorado’s offense has been anemic on the road, but still a solid performance, so perhaps a second half resurgence is on the way.

The bottom line is that if you take Liriano’s wSL/C from last season at face value and extrapolate it into 2014, Liriano would have saved himself 9 runs; the difference between his current ERA of 4.43 and a projected ERA of 3.43. If he has his slider working in the second half to go along with an ever-improving change-up, would that number surprise you?

Francisco Liriano has always been a somewhat volatile pitcher, but his ability to generate swings-and-misses has been tantalizing people since before he entered the league. If Pittsburgh is going make a push towards the top of the NL Central, getting Liriano back into form will be paramount to that end. The initial signs after his return from a strained oblique look promising, but will he be able to keep it up? Only time will tell.

. . .

All statistics and tables courtesy of FanGraphs, Brooks Baseball and Baseball Savant.

Zach Fogg is a columnist for Beyond the Box Score, Purple Row and Mile High Sports. You can follow him on Twitter at @zachfoggsports.