Jackson, 28, is under team control through the 2011 season. The 2003 first-round pick out of Cal established himself as a fairly patient hitter with mid range pop over the 2006-2008 seasons, hitting a combined .292/.371/.450 with a .361 wOBA. Adjusting for park and league factors, Jackson’s lumber was 14 percent better than average (114 wRC+). That’s not overwhelming for a guy who mainly manned first base, but Jackson controlled the zone (10.1 BB%, 12.8 K%), showed adequate power (.158 ISO) and improved his fantasy appeal by qualifying in the outfield during the ’08 season.
The past two years haven’t been nearly as kind. Jackson battled Valley Fever in 2009, limiting him to just 110 PA. He batted .182/.264/.253, with a .251 wOBA. Slowed by a right hamstring injury that required a DL stint in April, Jackson’s got a .298 wOBA and a .238/.326/.331 triple-slash in 172 PA this season. His ISO, .071 in 2009, hasn’t cracked triple-digits in 2010 either (.093).
In Oakland, Jackson figures to take over most of the playing time in left field. He’s worth a flyer in AL-only formats, but it’s hard to know how he’ll hit in the green and gold, given the uncertainty regarding his health. If Jackson is moving past the illness that sapped his strength, he could return to the .350-.360 wOBA range. Given that he has rated as about average in an outfield corner to this point, that would make Jackson a decent starting option for the A’s.
Mixed-leaguers probably want a player with higher upside and greater certainty, though. It’s also worth noting that Jackson will be moving from Chase Field, which (per the Bill James Handbook) increased run-scoring 15 percent and homers seven percent compared to a neutral park over the 2007-2009 seasons, to the Coliseum, which depressed runs nine percent and dingers 10 percent over the same time frame. That won’t help his chances of regaining fantasy relevance.
With Jackson no longer in the desert, Gerardo Parra will presumably get the majority of PT in left for the Diamondbacks. The 23-year-old lefty batter, rated as the 88th-best prospect in the game by Baseball America prior to 2009, has a .281/.319/.400 major league line in 609 PA over the past two seasons. The Venezuelan native has a .309 wOBA and a 82 wRC+, as he has rarely walked (5.4 BB%) or laced the ball into the gaps (.119 ISO).
Swinging early and often getting behind in the count (career 64.4 first pitch strike percentage, compared to the 58% MLB average), Parra has hit grounders at a 53.5% clip. He’s a good defender in an outfielder corner, but his offensive ceiling is subject to debate –Parra’s not uber-projectable at 5-11 and 195 pounds, and he didn’t display much thump in the minors (career .126 ISO). He was generally young for the levels at which he played, but Baseball America capped his home run power at the low-to-mid-teens, remarking that “if he has to move to an outfield corner he starts to look like a tweener.”
Demel, meanwhile, is expected to join a wretched D-Backs pen that ranks dead last in xFIP (5.16) and Win Probability Added (-6.88). A third-round pick in the 2007 draft out of TCU, Demel has missed lots of lumber as a pro (10 K/9) but has usually struggled to locate (4.5 BB/9). While the righty didn’t crack BA’s list of top 30 A’s prospects heading into 2010, Demel has added a cut fastball to his low-90’s fastball, changeup and erratic slider. In 28.2 IP with Triple-A Sacramento, the 24-year-old had 8.8 K/9, 2.8 BB/9 and a characteristically strong ground ball rate (49.4%; his overall GB% in the minors is 54.5). Demel’s worth monitoring, particularly if Arizona shops Chad Qualls to a team that focuses more on his very good track record and 3.56 xFIP this season instead of his bloated ERA.