Balfour had been engaged in bullpen sessions over the last week, but it wasn't until this week he was cleared to begin running again. That's the final step in his rehab process.
It's one that typically lasts from four to six weeks, putting Balfour on the shorter end of that spectrum, as the gritty reliever anticipated.
Balfour will likely have two weeks of exhibition action to prepare for the regular season.
Jane Lee is a reporter for MLB.com. Read her blog, Major Lee-ague, and follow her on Twitter @JaneMLB. This story was not subject to the approval of Major League Baseball or its clubs.