There was a time when Jackson was undeniably a solid contributor. His first full major league season was 2006, and as a 24 year old, he put up a 109 wRC+ (wRC+ is basically "a wOBA based version of OPS+. It’s park and league adjusted and it’s on a very similar scale as OPS+.") His wRC+ in 2007 was 115 and in 2008 it was 118. To put those figures into context, Rajai Davis' .305/.360/.423 line last year translated into a wRC+ of 119. So through his first three major league seasons, Jackson was a pretty good hitter, but didn't provide the ideal production you'd want from a first baseman or left fielder.
Disaster struck last year, though, as Jackson came down with a severe case of Valley Fever and didn't play at all after May 11. Not only did he miss months worth of at bats, his physical activity was extremely limited, to the point where he suffered substantial weight loss and atrophied muscles. Jackson was able to start the 2010 season, but its an open question as to how much of his hitting ability he's retained.
In 42 games so far he's hit just .238/.326/.331, "good" for a wRC+ of 76. These numbers are obviously unacceptable, especially from a corner outfielder playing half his games in Arizona. At this point, it's simply too early to tell if he's the same hitter he was before catching Valley Fever. In some ways he's the same hitter he was before last season. His plate discipline stats this year are more or less the same as his career averages; he's doing just as well at laying off pitches outside the zone, and making contact with pitches in the zone as he always has.
There also doesn't seem to be much of a problem with his batted ball statistics and his BABIP of .263 indicates that he's run into a bit of bad luck so far this season. The underlying data seems to back this up. His groundball to flyball ratio is the highest its ever been at 1.11 (in 2008 it was 1.04), and for a slow guy like Jackson that's a bad sign. However, he's made up for his decrease in flyballs by hitting more line drives, his line drive rate is 27%; in 2008 it was 21%.
The one thing that is obvious is that Jackson's power has yet to return. He has just 1 home run so far and his .093 ISO is a clear indication that something is wrong; Rajai Davis' ISO this year is .09. This lack of power is particularly disturbing, considering all the strength that he lost in his bout with Valley Fever. While his low BABIP may be the result of bad luck, it may also simply be that he's just not hitting the ball with any authority and the line drives he's hitting are the weak variety.
As an extra bat with a little bit of upside, Jackson's certainly not a bad addition, especially considering the "production" the A's have gotten out of their left fielders so far.
Given that the A's only gave up AAA reliever Sam Demel to get him (more on Demel tomorrow) and got cash to pay for part of Jackson's 2010 salary, this wasn't a bad deal. The A's aren't taking on a lot of risk, and if he continues to stink it up, they can just non-tender him after the season. If he rights himself at the plate and regains some power he's under team control for 2011.
The biggest risk in the deal would be for the A's to think that the addition of Jackson is the cure for the offense. In all likelihood, he's a slight upgrade over Patterson and Gross, and there's the risk that he's just as disappointing. I really hope this doesn't preclude the A's from making a bigger splash down the line because the A's offense needs more than a marginal upgrade if they want to stay in the AL West race.