Nats sign Jackson, shopping Lannan

The Washington Nationals, even after acquiring left-hander Gio Gonzalez and signing him to a five-year, $42 million extension, are not done adjusting their starting rotation.

The team has reached agreement with free-agent right-hander Edwin Jackson and is aggressively shopping left-hander John Lannan, major-league sources say.

The deal with Jackson, expected to be for one year in the $10 million range, is contingent on Jackson passing a physical.

Jackson, 28, is represented by Scott Boras, with whom the Nationals have worked well in the past. The Nats previously tried to acquire Jackson in trades, most notably at the 2010 non-waiver deadline.

Lannan, 27, lost his arbitration case with the Nationals but became the team’s highest-paid pitcher for 2012 on Thursday, receiving $5 million. He had asked for $5.7 million after earning $2.75 million last season.

If the Nationals traded Lannan, who went 10-13 with a 3.70 ERA last season, they still would have one left-hander in their rotation, Gonzalez, and possibly a second, Ross Detwiler.

Jackson, who has averaged nearly 208 innings and produced a 3.96 ERA over the past three seasons, would combine with Stephen Strasburg and Jordan Zimmermann to give the Nats three power right-handers. Chien-Ming Wang is another right-handed candidate for the team’s rotation.

Jackson has received multiple three-year offers, sources say, but by accepting a one-year deal he could go back on the market next offseason.

Signing with a team in the more pitcher-friendly National League would give him a better chance to enhance his value than if he went to an AL club such as the Boston Red Sox.

Jackson would become the latest Boras client with the Nationals, joining Strasburg, second baseman Danny Espinosa and outfielders Jayson Werth and Bryce Harper, among others.