Martin Perez's Changeup: The Real Deal?

Tuesday night, Texas Rangers starter Martin Perez tossed six innings against the Orioles holding them to two earned runs on six hits, four strikeouts and one walk. Since his 2013 debut on May 27, he's made five starts and the victory moved him to 3-1 this season. His ERA now sits at an impressive 2.08, the lowest among American League southpaws.

2013 is not 2012

After four years in the Rangers' farm system as a starter, the organization wasn't sure what the future held for the still just 22-year old Perez. Last season, he struggled over six starts with the big club posting a 5.88 ERA  and 1.73 WHIP .

But something changed for him pitching for Round Rock Triple A to start this season posting a 1.75 ERA and a 1.028 WHIP.

Rangers third-baseman Adrian Beltre told ESPN Dallas' Jeff Seidel that Perez is "a different guy" than they saw last season, and that he is "attacking the strike zone" much more. Increasing his strike zone percentage from 47.7 percent last season to 51.4 percent thus far in 2013, Beltre is absolutely correct.

More than any other pitch, the difference is Perez's changeup.

Perez changeup frequency over last two seasons vs. righties

As you can see, last season Perez had trouble finding consistency commanding his changeup against right-handed hitters. This season, his command of the pitch has improved noticeably, pinpointing the low-and-outside corner of the zone with consistency.

Take a look at the difference

Because Perez has proved capable of locating the pitch so consistently, opponents have become more willing to expand the zone and chase his changeups outside of the strike zone.

Last season, that wasn't the case. He threw fewer changeups in the strike zone and batters were less inclined to swing at changeups located out of the zone.

Opponents' swing rate on Perez's changeup located out of the strikezone

Because Perez struggled to command his changeup last season, right-handed hitters offered at only 24.6 percent of those located out of the zone. This season, that swing rate has increased dramatically to 42.2 percent and has directly impacted right-handed batters' success against the pitch. 

	2012	2013
Zone%	37.3%	49.4%
Chase%	24.6%	42.2%
SLG	.360	.290
BABIP	.333	.182
WHAV	.160	.097

Since his May 27th debut: 

• Perez is throwing more changeups for strikes and generating more frequent swings on out-of-the-zone changeups. Consequently, right-handed hitters have not enjoyed the same amount of success this season as they did in 2012.
• Perez's .182 BABIP on changeups ranks as the second-lowest among left-handers.
• His .097 WHAV and .290 opponent slugging percentage are enough for 11th-best against right-handers.  

What does this all mean?

Because of that changeup, Perez is quickly becoming one of the best young left-handed starters in baseball. His refined command of the pitch within the zone has held right-handed batters in check and tempts batters to swing at it even out of the zone.

With the Rangers' shaky rotation, Perez has offered consistency and can continue to do so if he continues to fool batters with this powerful, and often underrated, pitch.