Lowrie suffered a sprained right ankle Saturday afternoon in a collision at second base. The 28-year-old, who is batting .253/.343/.456 with 14 home runs on the season, also damaged a nerve in his leg.
Castro, 25, had been dealing with soreness in his surgically repaired right knee for some time, but the team decided to wait until after the All-Star break to make a move in case the soreness subsided. The catcher's move to the DL is retroactive to July 8.
Marwin Gonzalez and Carlos Corporan have been promoted to temporarily take over for Lowrie and Castro, respectively.
Will Lowrie miss more than the required 15 days?