Ryan Zimmerman. (Photo by Justin Edmonds/Getty Images)

Ryan Zimmerman took the first step, albeit a small one, in his recovery from a Grade 3 hamstring strain on Monday. According to Nationals Manager Matt Williams, Zimmerman did light walking on an underwater treadmill on Monday after two weeks of rest.

“He came out of it and said he felt fine,” Williams said. “It’s not high stress. But it’s part of his progression as he works through.”

Zimmerman’s next step will to do more light walking on a new machine, an anti-gravity treadmill that lightens the weight on his legs. Zimmerman’s progression will be long and slow, but Williams said he was encouraged that Zimmerman at least took the first step in strengthening his hamstring without any issue.

Zimmerman hurt his right hamstring on July 22 in Denver running to first base. Other admitting that Zimmerman’s hamstring strain was substantial, the Nationals have provided few details of the injury and a timetable. But on Tuesday, General Manager Mike Rizzo confirmed that Zimmerman has a Grade 3 strain and will be out six weeks.

Grade 3 is the most severe hamstring strain, meaning Zimmerman suffered a tear in the leg muscle. Zimmerman’s hamstring, however, is not completely torn. The Nationals have hoped that the muscle responds well to treatment and strengthening.

If Zimmerman misses only six weeks, he could perhaps be ready to return around the first week of September. The Nationals traded for Asdrubal Cabrera last week to help fill the infield void created by Zimmerman’s injury.

Rizzo declined to comment when asked if Zimmerman would return before the end of the regular season. Williams said he hoped Zimmerman would be back for the regular season.

“I believe so,” Williams said. “I would love to have that happen. He’s working hard to get back, as hard as he can at this point.”