Zimmerman suffered a hamstring injury last night when running out an infield grounder in the sixth inning. So it looks like the 44 games he already missed this year because of a fractured thumb won't mark his only time on the DL.
Zimmerman returned from the thumb injury on June 3 and has heated up of late, batting .387/.437/.613 with 10 extra-base hits and 17 RBIs in his last 17 games.
Walters, 24, is hitting .300/.358/.608 with 18 doubles, five triples, 15 homers and 48 RBIs in 60 games with Triple-A Syracuse. He has batted .182 with three homers and four RBIs in 27 games with the Nationals this season.
Without Zimmerman in the lineup, Anthony Rendon is at third and Danny Espinosa is at second. Outfielder Jayson Werth is also sitting out this afternoon's series finale with Scott Hairston starting in left.
Jose Lobaton is catching Stephen Strasburg for the day game after a night game.
Update: The Nats have made the move official, placing Zimmerman on the DL and calling up Walters.
It'll be quite a hit to the Nats, especially with Zimmerman's production of late. Zimmerman's importance can't be understated.
When he has been in the Nationals lineup this season, they are 33-19 and average 4.9 runs per game. In the 46 games they have played without him, the Nationals averaged 3.5 runs per game and went 22-24.
For the Nationals
CF Denard Span
LF Scott Hairston
3B Anthony Rendon
1B Adam LaRoche
SS Ian Desmond
RF Bryce Harper
2B Danny Espinosa
C Jose Lobaton
RHP Stephen Strasburg