What's Going On With: Francisco Liriano

Year	Age	Tm	Lg	W	L	W-L%	ERA	G	GS	IP	H	ER	HR	BB	SO	ERA+	WHIP
2011	27	MIN	AL	9	10	.474	5.09	26	24	134.1	125	76	14	75	112	80	1.489
2012	28	TOT	AL	6	12	.333	5.34	34	28	156.2	143	93	19	87	167	78	1.468
2013	29	PIT	NL	16	8	.667	3.02	26	26	161.0	134	54	9	63	163	117	1.224

Provided by Baseball-Reference.com: View Original Table
Generated 1/30/2014.

What's The Story? The Pirates plucked Francisco Liriano off the scrap heap. As you can see, he was a pretty bad pitcher in 2011 and 2012, compiling 5+ ERAs both years. ERA+, which measures ERA relative to the rest of the league, adjusted for home park, says he was 20% worse than average in 2011 and 22% worse in 2012, when he split time between the Twins and White Sox. Then he broke his right (non-pitching) arm in the off-season. The Pirates signed him for $1 million, and for that $1 million, they got one of the ten best left-handed starters in the National League. He went from being 22% below average to 17% above average, per ERA+. How did he do that?

If You Don't Want to Read All the Rest of This: He stopped throwing his fastball, which wasn't all that great a pitch anyway. As a result, he became a ground-ball machine in front of a Pirates defense that was one of the best in baseball at positioning themselves for balls hit on the ground. Fewer fly balls also meant fewer balls leaving the park. 

What's He Throwing?
Against Lefties:
Year   Fastball  Sinker    Slider   Change
2011      21%     39%       39%        0%
2012      20%     34%       46%        0%
2013       0%     53%       45%        2%

Against Righties:
Year   Fastball  Sinker    Slider   Change
2011      27%     22%       26%       25%
2012      23%     26%       29%       22%
2013       0%     38%       27%       35%

Overall:
Year   Fastball  Sinker    Slider   Change
2011      25%     26%       29%       19%
2012      22%     28%       33%       17%
2013       0%     41%       37%       22%

"Francisco, he're's the deal. Your fastball sucks. Stop throwing it." Can you imagine the conversation that went on? OK, technically, a "fastball" is a four-seam fastball and "sinker" is a two-seam fastball. But still. The four-seamer is the key pitch in most pitchers' repertoires. He relied on his sinker a lot more and also threw more changeups. He threw more sliders overall but that's because he faced more left-handed batters.

What's Wrong With His Fastball?
Miles Per Hour:
Year   Fastball  Sinker    Slider   Change
2011     91.6     91.8      85.4     84.1
2012     92.9     92.9      85.6     85.7
2013              93.0      86.9     86.5

Well, I suppose that when your fastball and sinker have basically the same velocity, you might as well go with the pitch that has more movement. Everything was a little faster last year.

What He Gave Up:
2011             Whiff/                   HR/

Year      Swing% Swing% GB%   LD%   FB%  FB+LD
Fastball   21%    11%   34%   14%   38%    9%
Sinker     20%    12%   55%   15%   28%    7%
Slider     36%    43%   50%   14%   28%   11%
Change     32%    43%   57%   12%   27%    3%

2012             Whiff/                   HR/

Year      Swing% Swing% GB%   LD%   FB%  FB+LD
Fastball   33%     9%   35%   20%   43%   13%
Sinker     38%    18%   50%   21%   21%    2%
Slider     55%    43%   41%   19%   31%   10%
Change     43%    44%   49%    8%   38%   12%

2013             Whiff/                   HR/

Year      Swing% Swing% GB%   LD%   FB%  FB+LD
Sinker     36%    14%   52%   23%   23%    7%
Slider     50%    42%   52%   24%   29%    3%

Change     53%    35%   55%   30%   12%    0%
(see glossary at end for column definitions)

Three things stand out about that fastball: They didn't generate a lot of swings-and-misses (15%-20% less than the typical lefty), it's his only pitch that didn't get hit on the ground a lot, and when it was hit in the air, it went over the fence a fair amount.

Why Did He Make the Change? Recall this post, where I linked to an article from the Pittsburgh Tribune describing how the Pirates last season used data to shift their fielders around based on opposing hitters' tendencies. However:

Shifts are only as effective as the number of groundballs hit into them. The second prong of the Pirates' comprehensive run prevention strategy was tied to increasing their pitchers' groundball rates. Defensive change began on the mound. 

How do pitchers produce groundballs? They must throw effective two-seam fastballs.

Two-seam fastballs are sinkers. Fewer fastballs that produce fly balls, more sinkers that generate grounders. Liriano's change in repertoire was in keeping the Pirates' strategy. Among his teammates, A.J. Burnett threw 25% fastballs and 36% sinkers in 2012. Last year his split was 22%/37%. Jeff Locke hardly threw his sinker at all (7% of pitches) in 2012, he threw it 29% of the time last year. Charlie Morton threw his sinker a lot on 2012 (42% of pitches) but he threw it more last year (57%). Reliever Mark Melancon doesn't have a sinker, but he used his curve and cut fastball more, both of which produce grounders, while reducing his proportion of fastballs from 31% in 2012 to 7% in 2013. Liriano was just the most dramatic case.

What Does the Future Hold? Liriano was historically good against left-handed hitters last year. Among lefties with 25+ starts, he allowed the fifth-lowest batting average (.131), second-lowest on base percentage (.174), second-lowest slugging percentage (.142) and lowest OPS (.321) in history against left handed hitters. His slider was unhittable by lefties: in 79 at bats, he allowed four singles and a double and got 35 strikeouts. That won't last. On the other hand, his batting average on balls in play, often an indicator of luck, was .292 compared to a league average of .296. Only 4.6% of his fly balls left the park, compared to a league average of 7.1%, so he'll probably regress some there. A few more homers, less dominance against southpaws...still no reason to think he won't be a fine pitcher again in 2014.

(All data here from Brooks Baseball and Baseball-Reference.) 
Glossary: Swing% = percentage of pitches at which batters swung; Whiff/Swing% = percentage of swings that missed the ball; GB%, LD%, FB% are percentage of batted balls that are ground balls, line drives, and fly balls, respectively; HR/FB+LD = percentage of fly balls and line drives that are home runs