Chris Volstad, who just turned 25 at the end of this past season, was drafted out of high school with the 16th pick in the 2005 draft. In 2006, he was named the Marlins' #1 prospect by Baseball America, and just cracked the Top 100 prospects list - he came in at 97. In 2007, he jumped up the Top 100 prospects list and landed at #40, subsequently falling to #58 in 2008.
I'll be looking at each year of Volstad's career, so the following chart should help you follow along.
Volstad was called up to the majors in 2008, and has had mixed results since. In the 84.1 innings that he pitched in 2008, Volstad put up a 2.88 ERA/3.82 FIP/4.55 xFIP line, which was worth 1.5 WAR. As you could probably tell by his line, he was pretty lucky in 2008. His .271 BABIP, (career average .295 BABIP), and 3.9% HR/FB, (career average 12.3% HR/FB), have been the lowest of his career, while his 77.1 LOB%, (career average 70.4% LOB%), has been the highest of his career.
His luck dried up in 2009 - he actually ended up being unlucky - and he posted a somewhat atrocious line: 5.21 ERA/5.29 FIP/4.29 xFIP and a .3 WAR in 159.0 innings pitched. While his BABIP and LOB% came closer to his career averages - and league averages - his HR/FB% spiked to 17.5%. To put that a couple of different ways: his HR/9 increased from .32 to 1.64; he gave up 3 HRs in 2008 and 29 HRs in 2009, (albeit in roughly twice the innings).
In 2010, his line improved to the tune of a 4.58 ERA/4.34 FIP/4.43 xFIP due in large part to his decreased HR/FB rate.
While Volstad's HR/FB spiked once again in 2011, he had arguably his best year in the majors from a peripherals standpoint. Volstad posted his best K/9 and BB/9 numbers, 6.36 and 2.66 respectively, and he induced ground balls at a very high rate of 52.3%, which according to 2010 league numbers, would rank close to the 90th percentile amongst all qualified pitchers.
While some may be concerned about how his HR/FB and HR/9 numbers will translate to Wrigely Field, here is a collection of statistics, statements, and images that should help quell your fears. HR/FB rates are highly variable from year to year and tend to regress toward league average, so Volstad will likely have a lower HR/FB rate moving forward. In terms of Park Factor, Sun Life Stadium had a .991 runs factor, while Wrigely had a .934 runs factor in 2011. Furthermore, Sun Life Stadium's HR factor was .941 while Wrigley's HR factor was .987, not a terribly large difference, and one that could be offset in the aggregate by the aforementioned difference in runs factor. The last reassuring point will come in the form of the following image:
The above image maps all of the hits and outs Chris Volstad recorded at Sun Life Stadium onto Wrigley Field.* Of the seven home runs that Volstad gave up at Sun Life Stadium, five would have been home runs at Wrigely, (I'm counting the one that's on top of the left field wall as a home run), and only one non-home run in Sun Life Stadium would have been a home run at Wrigley, (the double to deep center field). So, of the hits and outs that Volstad recorded at Sun Life Stadium, he gave up 7 home runs at Sun Life, which would have theoretically been 6 home runs at Wrigley. Volstad's move to Wrigley should not result in an increase in his HR/FB rate; in fact, Volstad will likely have a lower HR/FB rate going forward.
If Volstad continues to improve upon his K/9 and BB/9 numbers, and if his BABIP and HR/FB rates regress to the average - which isn't a huge "if" - he could become a very valuable middle of the rotation starter over the course of the next three years. In my opinion, Volstad is a pretty impressive return for Zambrano given the situation. Well done, TheoJed.
* These plots are taken from Gameday hit-location data, which track where the ball was fielded, not where the ball landed.
Thanks to MLB Gameday BIP Location.