The Twins could have catcher Joe Mauer back in the lineup by the end of April. Mauer will begin a running program this week, which could be the final step in his return from an inflamed sacroiliac joint. "He's catching. He's throwing a lot during infield practice. He's hitting with the minor leaguers," general manager Bill Smith said. "He's running in a swimming pool, and he's working on a treadmill."