Rule 1a of the offseason: There's always a mystery team. And in case you haven't noticed, the mystery team is often the team that gets their man. The two top free agents of the offseason were nabbed by the mystery team, for example. And the mystery team is at it again, this time in Washington D.C.:

The (Washington Nationals are) aggressively shopping left-hander John Lannan, according to major-league sources. Trading Lannan would clear payroll, potentially enabling the Nats to sign one of the top remaining free-agent right-handers, either Roy Oswalt or Edwin Jackson.

Rosenthal later clarified the story, suggesting that it's Jackson that the Nationals are targeting. The Nationals just won their arbitration case over Lannan, and he'll make $5 million next year. The lefty had a 3.70 ERA last year (104 ERA+), and he's been a fairly consistent innings muncher since becoming a full-time rotation member in 2008.

Acquiring Jackson, though, could give the Nationals four highly regarded starting pitchers younger than 30, and depending on the length of an Edwin Jackson contract, they'd all be locked up for the next two or three years. Of course, the same would apply if they kept Lannan, but perhaps the Nationals think that Jackson offers more upside.