The Pittsburgh Pirates placed rookie pitcher Zach Duke on the 15-day disabled list Saturday with a sprained left ankle. The move is retroactive to August 24. Duke, who injured the ankle while running the bases during this past Tuesday's game against St. Louis, has gone 6-0 with a 1.81 ERA in 10 starts since being called up from Triple-A on July 1. He is the first Pirates starting pitcher in club history to win each of his first six decisions. To fill Duke's roster spot, the Pirates purchased the contract of 23-year-old pitcher Paul Maholm from Triple-A Indianapolis. The southpaw is 7-3 with a 3.30 ERA in 22 starts minor league starts in both Triple-A and Double-A Altoona.