Blanks had been playing with a left calf strain, but he was forced to go on the 15-day DL when he aggravated it during a June 22 game against the Red Sox. He had recently begun taking swings, but in light of the MRI results, Melvin said there is no timetable for his return.
Since being traded to the A's from San Diego on May 15, Blanks is 15-for-45 (.333) with two home runs and a .446 on-base percentage. He has appeared in 20 games at first base in addition to a couple of corner outfield appearances.
The setback for Blanks could mean an extended opportunity for first baseman Nate Freiman, whom the A's recalled Sunday after Josh Reddick (right knee strain) returned to the DL.
Aaron Leibowitz is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.