The Astros have released pitcher Zach Duke and veteran hitter Jack Cust. Duke, 28, was an All-Star left-hander for the Pirates in 2009. He appeared in four games this spring, giving up 25 hits including five home runs in 14 1/3 innings. Cust, 32, has 105 major league home runs, 84 of them for the Athletics between 2007 and 2009. He had an elbow injury this spring and hit 1-for-25 in 11 games.