The Curious Case of Matthew Guerrier

In 2006, the Twins had Matt Guerrier supply 69.2 innings of low leverage relief work, performing adequately evident by his 3.77 Runs Allowed Average.  His overall season totals would have been much better had September been extracted.  In that month, Guerrier threw 23.1 innings (including one start) and allowed seven of his nine home runs along with an opponent slugging percentage of .549.  No matter, the following season Guerrier began like September of 2006 never happened.  In his first 15 innings, Guerrier limited opponents to a .122 BA.  Through June 24th of 2007, Guerrier held opponents to a .164 BA and had a decent 33-to-11 K-to-BB ratio.  This performance coupled with the losses of Dennys Reyes, Jesse Crain and Pat Neshek gave Guerrier the opportunity to pitch in high leverage situations.  In 2006, his leverage index was 0.50 but increased to 0.93 at the conclusion of 2007.  But with the added responsibility came the added challenges of retiring better hitters.  In the first half of the season, Guerrier had a 1.70 Runs Allowed Average supported by a .183/.246/.253 opponent batting line and surrendered just two home runs.  Following the All Star break, Guerrier's numbers were in flux.  His RAA ballooned to 3.34 from the 1.70 in the first half and opponents hit .272/.318/.463 while smacking seven home runs.   

 

Similar to 2007, the Twins were put in a situation without Neshek, this time early in the season.  Once again manager Ron Gardenhire turned to Guerrier and had him fill the majority of those high leverage situations (1.27 in 2008, up from 0.93).  In 51 innings in the first half of the season, Guerrier posted a 3.70 RAA with a 38-to-21 K-to-BB ratio.  In 217 plate appearances opponents hit .241/.315/.374.  Once again after the All Star break Guerrier found himself in another precarious situation where he was getting pummeled.  In the ensuing 25.1 innings, he held a 9.32 RAA and allowed seven home runs with a .336/.417/.582. 

 

This sort of drop-off in production was previously reserved for Juan Rincon.  So what are the factors behind the 29 year old's decline? 

 

Matt Guerrier is essentially a three-pitch pitcher, the first of which is the most common among relievers' arsenals, the fastball.   

 

Fastball	MPH	Usage	Zone	WHIFF	Batted Ball Outs %
2007	92.1	60.8%	63.1%	.185	66.1%
2008	92.4	67.%	42.8%	.048	67.5%

His fastball ranges from 90-94 but has averaged 92 the past two seasons. Though not predominantly an out-pitch, Guerrier's 2007 WHIFF of .185 was fairly decent by the fastball standards among relievers.  (For those unfamiliar with this metric, WHIFF average is the measurement of swing-and-misses on a particular pitch.  In this instance, the data is extracted from Josh Kalk's Pitch f/x database.)  What stands out in this comparison of his past two seasons, is the zone presences and his WHIFF effectiveness.  In 2007, Guerrier located the pitch within the zone 63% of the time, establishing an early strike.  One year later, Guerrier struggled to find the zone with his fastball in fewer than half of the times he threw it (42.8%).  It is no small wonder that in turn his WHIFF decreased to .048 and his walk rate spiked from 5.9% in 2007 to 10.7% in 2008.

   

Curveball	MPH	Usage	Zone	WHIFF	Batted Ball Outs %
2007	80.0	17.4%	51.4%	.348	60.0%
2008	80.6	10.1%	57.7%	.167	71.4%

 

Outside of his fastball, Guerrier implements a tight 12-to-6 curveball that is spun at a significantly slower rate, giving him an good off-speed breaking ball.  Averaging around a 12-mph difference in his two most used pitches, his curveball in 2007 was a very effective out-pitch, reflected in his .348 WHIFF rate.  This past season, Guerrier's use of his curveball was curtailed - most likely in response to being unable to find the strike zone with the fastball to properly set up the pitch - and with it his ability to induce misses dropped to .167.  That fact aside, the curveball was equally effective in that he was able to retire 71% of batters that put the pitch into play - a large boost from 2007. 

 

Slider	MPH	Usage	Zone	WHIFF	Batted Ball Outs %
2007	86.3	21.7%	67.8%	.364	60.0%
2008	86.6	20.9%	69.0%	.423	71.7%

 

To those that watch the Twins telecasts on FSN North, you would recall how much emphasis is placed on Guerrier's curveball.  Frequently overlooked by analysts, however, is the fact that Matt Guerrier's best pitch is his slider.  With a .423 WHIFF, his slider has one of the highest WHIFFs among the Twins' staff.  What makes this pitch exceedingly better is that he saves his deployment of the pitch for his right-handed counterparts.  The down-and-away spin action obtained numerous empty swings. 

For Guerrier to improve in 2009 he will have to refine the command of his fastball.  Being able to locate the fastball for a strike will do two things, (1) it will increase the amount of chases in Guerrier’s curveball from both sides of the plate and (2) it will cut down the number of total pitches leading to a more productive second-half. The success of his curveball, his secondary pitch against lefties, is directly correlated with his ability to throw the fastball for a strike consistently.  According to billjamesonline.net, in 2008 Guerrier relied on his fastball against the lefties (62% usage) and had a lowly 16-to-15 K-to-BB ratio.  Limited to two pitches against his left-handed counterparts, those opponents were able to coax walks and sit on hanging curveballs without having to answer to a 93-mph fastball cutting the plate in half at the knees. 

 

Another often cited explanation for Guerrier’s late season breakdown is that he has had a burdening workload in the past several years.  Though his appearances have risen steadily over the past four seasons, his increase has actually been a byproduct of his own doing.  In 2005 Guerrier faced 306 batters and used 1,094 pitches (3.58 per PA).  In 2006 Guerrier’s appearances decreased from 43 to 39 while his total batters faced actually decreased to 300 but used roughly the same amount of pitches (1,071 or 3.57 per PA).  With a depleted bullpen, Guerrier was asked to step up his use from 39 to 73 in 2007 but ultimately faced just 51 more batters -- a 17% increase to his prior workload –- and Guerrier needed approximately 3.69 pitches each plate appearance and threw 1,296 total.  This past season Guerrier needed a whopping 1,320 pitches against a pool of 344 leading to a grossly inefficient 3.83 pitches per plate appearances during his 76 outings.  By establishing his fastball consistently Guerrier would shave several pitches off each plate appearance and whittle down the total amount leading to late season success.