After beating John Lannan in an arbitration hearing this week, the Nationals are now aggressively shopping the left-hander according to Ken Rosenthal and Jon Paul Morosi of FOX Sports. The move would potentially clear $5MM in payroll, and Rosenthal says (on Twitter) they are targeting Edwin Jackson (not Roy Oswalt). Signing Jackson is contingent on trading Lannan, he adds. The Nationals would like to get a position player in a trade for Lannan, MLB.com's Bill Ladson tweets.

Gio Gonzalez, Stephen Strasburg, and Jordan Zimmermann are locks for Washington's rotation, and Chien-Ming Wang is a safe bet as well given his $4MM salary. That leaves Lannan and Ross Detwiler for the final spot, though Detwiler is out of options. He could potentially shift to the bullpen if the team is able to move Lannan and sign someone like Oswalt or Jackson.

Lannan, 27, is the team's highest paid pitcher. He posted a 3.70 ERA with 5.2 K/9 and 3.7 BB/9 in 184 2/3 innings last year. It marked the third time in four seasons that he has started 30 games, pitched 180-plus innings and kept his ERA under 4.00. He will be under team contract as an arbitration-eligible player in 2013.