Miller has three innings in a pair of relief appearances since his last start on July 31, and he was scheduled to throw an extended side session on Wednesday.
"Well, we'll certainly keep an eye on him," said manager Terry Francona. "He's thrown, warmed up a lot. He hasn't necessarily been in games, so it shouldn't get in the way."
Francona said Miller will probably throw 85-95 pitches on Friday, but Miller hasn't completed six innings since July 2.
"I just think you come out of that start probably a little more sore than normal," Francona said. "Or stiff is probably a better word."
Jason Mastrodonato is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.