"Once he gets sore, then we got to shut him down for a few days," manager Matt Williams said. "So we don't want to get there."
McLouth, 33, had surgery on his right shoulder in August to repair a torn labrum and missed the rest of last season. On Saturday, he played catch at 120 feet to help stretch out his arm.
"Get my motion, get my mechanics back," he said. "When it was bothering me, I got into some bad habits to try to guard it from hurting when I threw."
McLouth's shoulder has not hindered his progress at the plate, so he should be ready once he completes the throwing program. He was not sure if he would be ready to play Thursday once the Nationals begin Spring Training games, but if not, he said his debut would be soon after.
McLouth is the likely starting left fielder for the Nationals' season opener on April 6 against the Mets, if Jayson Werth (offseason shoulder surgery) is not ready by then.
"It doesn't hurt, and nothing I've done has made it hurt at all," McLouth said. "So it's fine. Now it's just a matter of getting more distance."
Jamal Collier is a reporter for MLB.com. Follow him on Twitter at @jamalcollier. This story was not subject to the approval of Major League Baseball or its clubs.