By Joseph Salvador Carolina’s star running back is dealing with a quad issue. View the original article to see embedded media. With Christian McCaffrey’s availability in question this Sunday, Baker Mayfield had a little fun when talking to reporters about his star running back’s possible return. It appears even he doesn’t know when his best weapon is returning to the field but he’s optimistic. “He’s gone zero dark 30 on us, keeping us guessing,” Mayfield told media members Thursday. Mayfield added he’s preparing as if McCaffrey is suiting up. The 26-year-old has been dealing with a quad injury…