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8/6/2014 1:10 A.M. ET

Zimmerman runs on water treadmill

WASHINGTON -- Ryan Zimmerman (Grade 3 right hamstring strain) ran on a water treadmill Monday as the first step in his rehab and strengthening process, Nationals manager Matt Williams said. The third baseman reported feeling fine following the session.

"It's really light. It's just walking," Williams said Tuesday. "But it's more than you would normally do getting out of bed and getting in the car and driving to the ballpark."

The next step for Zimmerman will be running on the team's AlterG anti-gravity treadmill, which allows a player to run with a percentage of his body weight taken off, according to Williams. The team will start Zimmerman off light on the AlterG and slowly build him up as part of a "long progression."

"Of course it's encouraging," Williams said. "It's not high stress by any stretch. But it's part of his progression as he works through it. So he'll take the next step and another one and another one and another one."

Williams said he believes the Nationals will see Zimmerman in the lineup before the end of the regular season, a notion general manager Mike Rizzo confirmed Tuesday.

Rizzo said the right-handed slugger could be back after a six-week recovery.

"I would love to have that happen," Williams said. "He's working hard to get back, as hard as he can work at this point. So I would hope so."

Slumping Harper lets out frustration vs. Mets

WASHINGTON -- In his third at-bat during Tuesday night's 6-1 loss to the Mets at Nationals Park, Bryce Harper skied an 0-1 fastball from right-hander Zack Wheeler to deep left field. The pitch was located down and away, but Harper was able to square the barrel of his bat to the ball, sending it soaring toward the blue seats.

But the well-struck ball fell short, and left fielder Eric Campbell secured the catch on the warning track for the final out of the sixth inning as Harper rounded first base. In frustration, the left-handed slugger took off his helmet and smashed it to the ground. The sound could be heard around the stadium.

"I'm OK with it," manager Matt Williams said of the outburst. "We've all been there. We've all been in that position where it looks like somebody's throwing an aspirin up there. But it can turn quickly, too, and some days it just looks like a beach ball as well."

Harper finished the contest 0-for-4 with three strikeouts. He's now batting .214 since his return from the disabled list on June 30 after missing 57 games with a torn left thumb ligament. The 21-year-old has tried anything and everything to get comfortable at the plate during his recent slump, including a number of different stances that vary in hand placement and stature, but nothing has worked.

Nonetheless, Williams is in full support of Harper, largely because the outfielder continues to put forth the effort to improve.

"I'm fine with him," Williams said. "He's working hard. He works hard every day. He gets here, he's one of the first guys here to work. And he's working through it. So I'm good with it. He's grinding up there."

Ramos, wife welcome first child, a baby girl

WASHINGTON -- Wilson Ramos' wife, Yeli, gave birth to the couple's first child, a baby girl, on Tuesday morning in Washington, manager Matt Williams said. Ramos began his three-day paternity leave on Tuesday and was with his wife at the hospital.

"He's anxious about it. He's got a number of family members in town. So he's excited and nervous and I'm sure he didn't get any sleep last night. But everybody seems to be fine," Williams said. "Everybody's recovering. So we'll see how it goes from here. But I'm sure he's very proud today."

Williams wouldn't confirm whether Ramos would take the full three days before returning to the Nationals. For now, the team will take it day by day.

In the meantime, catcher Sandy Leon was recalled from Triple-A Syracuse and took Ramos' spot on the 25-man roster. Leon is well acclimated with the Major League team, considering he served as the backup catcher during Ramos' two stints on the disabled list this season -- one for 32 games in April because of a left hamate fracture and the other for 14 games in June with a right hamstring strain.

Leon said it's difficult to transition from playing every day in the Minors to taking on a bench role in the big leagues, but he spends a lot of time in the batting cage to maintain his timing and stay sharp.

"It's kind of hard," Leon said. "But you've just got to keep working, do your routine and just be ready."

Daniel Popper is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.