Johnson (hamstring) threw from 120 feet off flat ground Monday and will pitch a bullpen session Tuesday, Brian MacPherson of the Providence Journal reports.
It's looking like Johnson may have avoided serious injury when he landed awkwardly while making a pitch for Triple-A Pawtucket on Saturday. If he makes it out of the bullpen without a setback, Johnson will be expected to fill in for Eduardo Rodriguez (knee) in the rotation Saturday. With Boston having announced that Rodriguez will rest for 3-to-4 weeks, Johnson has an opportunity to make his next five or six starts in the majors. The young left-hander has made two starts for Boston this season, most recently throwing a complete-game shutout against Seattle.