Hart drove the ball well in his hitting session, easily clearing the fence in left-center at Safeco Field several times before heading to the indoor cage to do some more work.
"I feel better," he said. "I haven't had any setbacks. I'm just doing the normal stuff. I want to make sure I don't go backward."
Hart missed all of last season following two microfracture knee surgeries while with the Brewers, so the two-time National League All-Star is all too familiar with the training room. He said this injury stint seems relatively tame in comparison as he figures to only be out a few more weeks, if all goes well.
"I'm used to worse things, so it's actually going pretty quick," he said. "It's coming along well. I don't see it being too much longer."
After working all spring to regain his timing following the missed 2013 season, Hart was batting .209 with five doubles, five home runs and 17 RBIs in 37 games before hurting his leg while stealing second base against the Twins.
Greg Johns is a reporter for MLB.com. Follow him on Twitter @GregJohnsMLB as well as his Mariners Musings blog. This story was not subject to the approval of Major League Baseball or its clubs.