
Over the past three years, Jackson has been traded five times. (Even Cliff Lee, who's played for four teams in the last two years, thinks that's a lot of movement.)
In 2008, fresh off making it to the World Series for the first time, the Tampa Bay Rays dealt him to the Detroit Tigers for outfielder Matt Joyce.
That was a relatively small transaction compared to what was to come.
Almost exactly a year later, during which he made his first All-Star team, the Tigers traded Jackson to the Arizona Diamondbacks in a huge three-team deal that involved Curtis Granderson, Max Scherzer and Ian Kennedy among seven players.
Seven months after that (or four months into the 2010 season), Chicago White Sox general manager Kenny Williams needed some starting pitching help to protect a 1 1/2-game AL Central lead and acquired Jackson from the D-Backs for pitcher Daniel Hudson and a minor leaguer. At the time, there were rumblings that Williams would flip Jackson to the Washington Nationals for Adam Dunn. That trade never materialized, however.
What happened to Jackson on Wednesday might have topped all of those previous deals. This time, Jackson was moved*twice in the same day.
With a perceived surplus of starting pitching, the White Sox traded him to the Toronto Blue Jays for reliever Jason Frasor and a minor league pitcher.
However, the Jays getting Jackson didn't make much sense. The team is out of contention and Jackson is in the final year of his contract. Clarity soon followed when Jackson was then traded to the St. Louis Cardinals in an eight-player deal that shipped outfielder Colby Rasmus to Toronto.
So why does this keep happening to Jackson? He's an extremely talented pitcher who throws hard, eats up innings, and from all accounts, is a good citizen and nice guy. Yet he continually gets treated like a used sofa in a college town, getting passed from place to place.
Here are five reasons why Jackson is the baseball equivalent of a hot potato:

Jackson is being paid $8.35 million this year, and the White Sox didn't want to pay the rest of that with concerns about their payroll. So he was dealt away for a cheaper reliever. With Jackson facing free agency after the season, it will be interesting to see if the Cardinals try to keep him or let him test the open market.
2. He throws how hard? Sure, I'm interested: Jackson is the kind of pitcher that makes scouts and general managers drool. He consistently reaches the mid-90s with his fastball, mixes that with a hard slider, and also shows a curveball and changeup. He's like the prototype starting pitcher that baseball people draw up in their dreams.
So when other teams find out that a guy like that is available, they pursue him. Jackson has never been the ace on any staff he's joined, but he has No. 1 pitcher stuff. Any team would take that on their roster.
3. Teams love cost control: This might seem to run contrary to the first point, since Jackson's salary has steadily increased since 2008. But Jackson had value to teams acquiring him with three arbitration years before free agency. Even if he received a raise to avoid arbitration, which is exactly what happened, it was still less money than Jackson likely would've received as a free agent. Getting a pitcher of Jackson's talent under a controlled cost is very appealing to most teams.
4. Good, but not great: As mentioned before, Jackson has never been considered the staff ace on whichever team he's been with. Sometimes, that's just been the way it works out. (Verlander is the Tigers' ace, Dan Haren was the D-Backs' best starter, and either Mark Buehrle or John Danks was seen as the top starter with the White Sox.)
Considering Jackson's talent, that's something of a disappointment. And that's probably made him expendable, knowing that he's just good enough —*with upside left to fulfill — to tantalize a team in need of a good starter and perhaps convince a pitching coach that he can tap that unrealized potential.
5. We have the final piece! Each of the teams Jackson has been traded to has either been in contention or expected to contend before the season. For a team that feels it needs one more pitcher to push them over the top — such as the Tigers —*or strengthen a starting rotation — as was probably the case with the White Sox —*Jackson makes an ideal candidate.
He fits either category for the Cardinals, who hold a 1/2-game lead in the NL Central. They need another starter, Dave Duncan surely feels he can work with that talent, and Jackson could help make a difference in a tight division race. He'll start Friday night.
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