Johnson (elbow), who is slated to throw a bullpen session Monday, is progressing well and threw off flat-ground on Friday, MLB.com reports. Johnson is less than a year removed from his second Tommy John surgery, but has been able to put in the rehab and flat-ground work this spring to move to throwing off a mound. If all goes well and Johnson continues to progress without any setbacks, he could be back in the major leagues by late May or early June.