The Los Angeles Dodgers placed outfielder Matt Kemp back on the 15-day disabled list on Thursday after he aggravated his hamstring injury, but Kemp said he expects to be sidelined for a month. Kemp is out of action again just two days after being activated from the disabled list. Kemp reinjured his left hamstring while running the bases in Wednesday's game. To replace Kemp on the roster, the Dodgers called up infielder/outfielder Alex Castellanos from Triple-A Albuquerque. Kemp is batting .355 with 12 homers. The Dodgers went 9-5 while Kemp was on the DL the last time.