The Washington Nationals have traded veteran starter Jason Marquis to the Arizona Diamondbacks this afternoon in exchange for Single-A shortstop Zach Walters, a ninth round pick in the 2010 draft.  The deal has not been announced by the team, but it is official according to multiple sources.

Marquis, 32, went 8-5 with a 3.95 ERA in 20 starts.  He will become a free agent at the end of the year and will not qualify for even Type-B free agency, meaning the Nationals would not have received compensation should he sign with another team.  Reports indicate Arizona was willing to assume the remainder of Marquis' salary this season, saving the Nats over $2.5 million.

Walters, a 21 year old middle infielder, was hitting .302/.377/.485 with Single-A South Bend, playing shortstop primarily, but also appearing at second and third base.  In 166 career minor league games, Walters has hit .302/.360/.465.  This is the second position player today the Nats have picked up with good on-base skills, joining OF Erik Komastu, acquired for Jerry Hairston Jr earlier in the day from the Milwaukee Brewers.

Marquis was due to start for the Nationals in tonight's game with the New York Mets.  His spot will be taken tonight by Yunesky Maya.  Maya went 0-1 with a 6.86 ERA in four starts earlier this season with the Nats.  But manager Davey Johnson indicated in his post-game press conference last night and reiterated today that the team may recall some younger arms from the minors after the trade deadline shakes out, including RHP Brad Peacock and LHP Tom Milone.

Major League sources are still indicating that the Nationals continue to be involved in talks for a Major League center fielder, with Denard Span of the Twins and Michael Bourn of the Astros the most likely targets.  Sources have indicated the Nats have been reluctant to include young, team-controlled closer Drew Storen in a deal for Span, but with Rick Ankiel the only center fielder on the Nats roster, speculation is running rampant at Nats Park and on the Internet.