Denver, CO -- (Sports Network) - The Washington Nationals placed outfielder Elijah Dukes on the 15-day disabled list Thursday with a strained right calf.

The move is retroactive to August 3.

Dukes, 24, is currently batting .264 with six home runs and 23 runs batted in during 54 games played this season. He has been on the disabled list twice before in 2008 with right hamstring and right knee issues.

To replace Dukes on the roster, Washington recalled Garrett Mock from Triple-A Columbus. Returning for his fourth stint on the major league roster, Mock has posted a 5.27 earned run average in 13 2/3 innings pitched this season, including two starts.