Frias (back) was placed on the 15-day DL Sunday, MLB.com's Ken Gurnick reports. Frias was originally scheduled to start Monday against the Phillies, but the team will now have to turn to a backup plan. Even though an MRI on his lower back came back negative, his status for that start had rightfully been up in the air. No official replacement has been announced yet, but long relief man Juan Nicasio could be one option.