The Washington Nationals have signed left-hander Zach Duke to a big-league deal, reports Amanda Comak of the Washington Times:

The #nats have signed LHP Zach Duke to a major league deal, according multiple sources.

— Amanda Comak (@acomak) December 3, 2012

The 29-year-old Duke was originally picked up by the Nats in late March following his release by the Arizona Diamondbacks.The left-hander -- who has not pitched a full season in the big leagues since his final year with the Pirates in 2010 -- spent much of 2012 at the Nationals' Triple-A affiliate in Syracuse, Illinois, where he posted a 3.51 ERA in 164⅓ innings across 15 starts.

Duke strong Triple-A numbers earned a shot with the big club when rosters expanded in September. He proceeded to post a 1.32 ERA in eight big-league appearances -- spanning 13⅔ innings -- allowing just two runs and striking out 10. With his strong showing in a short September call-up, Comak speculates that Duke will take on the long-man/spot starter role for the Nats in 2013.

The left-hander has pitched in parts of eight big-league seasons, and owns a career 4.52 earned-run average.