The left-hander is 3-4 with a 4.53 ERA in nine appearances, including eight starts.
"He was examined, and I think they want to have one more MRI, one more look to compare it to where he was like three weeks ago when they did it the last time," Black said. "So they're going to compare that and then see if he's good to go as far as getting back on a throwing program."
Tim Stauffer has pitched in Erlin's spot in the rotation.
Erik Bacharach is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.