FanGraphs: How Zito got his groove back

When the Giants signed Barry Zito to a seven-year, $126 million contract after the 2006 season, few thought he would live up to it. He was four years removed from his stellar Cy Young season at the time, and in the ensuing years had shown signs of decline. His strikeout rate declined, his home run rate increased, and his batting average on balls in play (BABIP) returned to league average after years of falling far below it.

In 2009, however, Zito experienced a turnaround of sorts. His strikeout rate rose to 7.22 per nine innings, his highest rate since 2001. His walks also dropped back to around his career rate (3.8 per nine), as did his home runs allowed (0.8). Along with this went his ERA, 4.03, much closer to his career average than his previous two seasons. And after shutting out the Astros for six innings last night, it appears Zito has been reborn. What changed for him?

Part of it was the return of his curveball, a weapon that failed him during his first two seasons in San Francisco. Another large part of his transformation came from an increased use of his slider. Zito started employing a slider in 2005 after performing poorly in 2004. He didn't throw it too often, never using it more than 8.5 percent of the time in 2005 or 2006. In 2009, however, he used it more than his curveball, throwing it 18.6 percent of the time against 18.2 percent with his curveball. During his 2010 debut on Tuesday night, Zito continued using his slider effectively.

Of the 90 pitches he threw, 11 were sliders, or 12.2 percent. He went to the changeup and curveball more often, though neither was as effective as the slider. Only one of the 11 sliders ended up outside the zone, and Zito generated three swings and misses off the slider, more than the changeup and curveball combined. Additionally, he threw eight of those 11 sliders in a two-strike count, signaling that it could be employed as his primary out pitch this season. In his six innings of work, the southpaw fanned six, walked one, and allowed just three hits in the Giants' 3-0 win.

It seems that Zito learned something during his poor 2008 season, when he had a career-high 5.15 ERA. That was when he started increasing his slider usage, and it proved his most effective pitch. In 2007, he threw his slider 4.3 percent of the time. In 2008, 9.8 percent and last year 18.6 percent. In his 2010 debut he employed his curveball and changeup more frequently, but picked his spots with the slider. It worked out for him. The slider is what turned Barry Zito back into an effective pitcher.

Joe Pawlikowski is an author of FanGraphs.