Atlanta Braves: Jair Jurrjens and His Date with Regression

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Atlanta Braves: Jair Jurrjens and His Date with Regression
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Jair Jurrjens turned in one of his worst starts of the season against the Nationals Monday night, allowing five earned runs on seven hits and one walk in five innings of work. He saw his ERA inflate from 2.38 to 2.63, and fantasy owners and Braves fans should expect some more of same types of outings over the final two months of the season. 

During his two best seasons in the majors, 2011 and 2009, his ERA's have outperformed his xFIP due to favorable strand rates and BABIP's. His .268 BABIP in 2009 and .263 BABIP this season indicate that some amount of luck has contributed to Jurrjens' performance. Furthermore, opposing hitters are hitting the ball harder off Jurrjens this season, as he has surrendered 21.1 percent line drives in 2011 compared to just 17.9 percent line drives in 2009.

A drop in velocity can explain the amount of hard hit balls put in play this season. From 2009-2010, Jurrjens' average fastball velocity was 91.1 mph, but he has seen that velocity drop to 89.1 mph this season. This drop has resulted in an overall drop in his swinging-strike percentage from 8.9 to 7.5 percent, as well as his lowest strikeout rate since being acquired by the Braves (5.73 K/9). 

Jurrjens has mostly benefited from a career-high strand rate of 81.9 percent this season, the fifth highest among qualified starting pitchers. And while he has stranded more runners this season, there is some evidence that he can keep his ERA below 3.00. He has improved his overall WHIP by lowering his walk rate from 3.25 to 2.36 BB/9, a career low, and his .263 BABIP and 7.5 percent home runs per fly ball are actually in line his career rates of .279 and 7.3 percent, respectively.

What will work agains Jurrjens is his history of slumping during the final months of the season. He has a career xFIP of 4.32 in August, and a 4.33 career mark in September/October. His BABIP usually increases during those months as well, and Jurrjens has shown a downward trend in velocity over his last three starts.

Expect his .263 BABIP to steadily increase over the coming weeks while his strand rate falls closer to the league average. He should finish his season with an ERA closer to 3.10, which should still put him among the top 30 starting pitchers, but Braves fans should not expect him to be in the Cy Young discussion.

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