Lannan, who was the opening day starter for the Nationals in 2009 and 2010, is 40-51 with a 3.99 ERA in six seasons with the Nationals. He has made two starts for the Nationals this season, winning both while allowing five earned runs in 13 innings pitched.
The Nationals also promoted catcher Sandy Leon and outfielder Eury Perez Saturday. The team also activated utilityman Mark DeRosa, who has hit .152/.288/.212 in 81 plate appearances this year, from the 15-day disabled list.
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