Pinpointing Edwin Jackson‘s value has been a hot topic of debate in the blogosphere, and among major league general managers, for the past three years.

In 2007, Jackson suffered through a seemingly miserable season, posting a 5-15 record and 5.76 ERA, the kind of stats that will torpedo a fantasy season. Turns out Jackson was the victim of bad luck and especially bad defense that year. Pitching in front of noted defensive sieves such as Delmon Young and Brendan Harris, Jackson yielded a stratospheric batting average on plays in play of .351. His xFIP (expected Fielding Independent Pitching, a stat that runs along a similar scale to ERA, but strips out the impact of defense, park effects and other factors outside a pitcher’s control) was nearly a run lower than his ERA, at 4.95. This was a roughly league average pitcher thrust into the worst situation.

In 2008, Jackson appeared to take a huge step forward. The big right-hander upped his record to 14-11, with a 4.42 ERA, delighting fantasy owners who gambled a late-round pick on him. But a closer look revealed that he hadn’t changed at all. Jackson owed most of the improvement in his superficial stats to a vast improvement in the Rays’ defense. According to Ultimate Zone Rating, a stat which tracks fielders’ ability to make plays in and around their assigned positions, the Rays moved from dead last in baseball in 2007 with a mark of -57.7 to first in 2008, at 74.2. Put another way: Every 10 positive UZR points add up to roughly one more win in the standings for a given team.

So Tampa Bay’s defense went from costing the team nearly six wins in 2007 to adding more than seven wins to the ledger in 2008. That’s a gigantic, 13-win improvement – one of the biggest year-to-year changes in MLB history – before any Rays pitcher made a pitch or any Rays batter took a swing. Indeed, Jackson’s xFIP actually rose from 4.95 in 2007 to 5.03 in 2008, as some of Jackson’s peripheral stats, including his strikeout rate, got worse. It seems impossible to believe that a pitcher could go from 5-15 to 14-11 and actually prove slightly less valuable to his team on a per-inning basis – but Jackson turned the trick.

After the ’08 season, Rays management saw a chance to trade a pitcher whose perceived value likely outshone his actual value, and that’s exactly what the team did – shipping Jackson to Detroit for promising outfielder Matt Joyce.

At first glance, Jackson’s debut season in Motown
could be seen as a major breakout: His ERA dropped nearly another full run to 3.62 (7th in the American League), his strikeout-to-walk ratio jumped over the key 2:1 mark, and Jackson gave the Tigers a career-high 214 innings pitched (also 7th in the AL). His xFIP slid to 4.39. Combine his increased innings total with his improved performance, and FanGraphs estimates that Jackson’s season was worth 3.5 Wins Above Replacement — or three-and-a-half more wins than a fringe major league pitcher — for Detroit.
 
Even in a very good season, Jackson still showed his share of flaws. First, Jackson’s season reveals a massive chasm between his first and second
half numbers. In the first half he was one of the American League’s
top pitchers, walking just 35 batters in 121.2 IP and compiling a 2.52 ERA. The
second half wasn’t as kind, as Jackson allowed more hits, runs, and
home runs while walking the same number of batters in nearly 30 fewer
innings. His full season marked of 1.14 homers allowed per nine innings was higher than average among qualified starters, a puzzling and troubling sign at Comerica Park, which suppressed homers by 2.6% compared to league average in 2009, and rates as a pitcher-friendly park compared to other MLB stadiums.

This off-season, Jackson was involved in another trade, this one sending him to Arizona. So, which Edwin Jackson should we expect to see in 2010?