The Dodgers have placed Matt Kemp on the 15-day disabled list Thursday, and the All-Star outfielder is expected to miss at least four weeks, according to team trainer Sue Falsone. Kemp aggravated his left hamstring Wednesday night, just two days after he came off the DL following a two-week stint there with a strain of the same muscle. To fill Kemp's roster spot, the Dodgers called up infielder-outfielder Alex Castellanos from Triple-A Albuquerque.