Straight from the horse's mouth:

The Washington Nationals today placed outfielder Elijah Dukes on the 15-Day Disabled List, retroactive to August 3, with a right calf strain and recalled right-handed pitcher Garrett Mock from Columbus of the Triple-A International League.   Nationals Senior Vice President and General Manager Jim Bowden made the announcement.

Mock returns for a fourth stint with the Nationals this season. To date, the rookie has posted a 5.27 ERA (8 ER/13.2 IP) in five games/two starts with Washington. During his most-recent stint with Washington, which came in late July, Mock fired 3.0 one-hit scoreless innings of relief spanning three appearances, during which did not issue a walk, fanned five and posted a batting average against of .091 (1-for-11).

The 25 year-old Mock was 6-3 with a 3.01 ERA in 19 games/17 starts for Columbus. Mock’s strikeout-to-walk ratio in the International League was a stellar 3.8/1 (96 strikeouts/25 walks), and he currently ranks fourth in the IL in ERA.

Dukes, 24, is batting .264 (48-for-182) with six home runs and 23 RBI in 54 games with the Nationals this season. Among those with 200 plate appearances, his .364 on-base percentage leads all Nationals. This is Dukes’ third trip to the Disabled List this season. His previous DL stints were due to right-hamstring and right-knee issues.

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UPDATE:  This from the Post:

An MRI exam of Elijah Dukes's bothersome right calf revealed a strain far more significant than the team first believed, and as a result, Dukes, the team's starting left fielder, will miss four to six weeks.

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