(Katherine Frey / The Washington Post)

Third baseman Ryan Zimmerman will sit out tonight in order to give his surgically repaired right shoulder a rest, but Manager Davey Johnson said Zimmerman will return tomorrow and could even pinch hit tonight against the Diamondbacks.

Zimmerman, hitting .269/.350/.463, did not appear in the Nationals’ clubhouse at the usual time and did not take batting or fielding practice with the rest of the Nationals.

Johnson said Zimmerman told him last week he was feeling “discomfort” in his shoulder and was looking for a spot to take a day off. Johnson determined it would be best to let Zimmerman sit today, thereby stacking Monday’s team off day with today’s personal day of rest.

“Zim’s fine,” Johnson said. “He does a whole lot of throwing. Even during the ballgame, he throws a lot. When you do that much work, sometimes you can get a little – I don’t want to call it dead arm, but something like that. This is just a good opportunity. Also, it gives me an opportunity for some of the guys who are starting to swing the bat a little bit better, get them in the game.”

In November, Zimmerman underwent surgery to repair an inflamed A/C joint in his right shoulder, along with fraying in his labrum and rotator cuff. Zimmerman played through the injury almost of last year with the help of multiple cortisone shots.

Zimmerman, Johnson said, has been taking anti-inflammation medication. “That’s just normal,” Johnson said. “Nothing earth-shattering.”

As Zimmerman came off the shoulder surgery, he has been on a strict throwing program all season. Starting in spring training, Zimmerman tried to return to a more natural, free throwing motion. His mechanics have come under scrutiny while he has committed a major league-high 10 throwing errors.

Zimmerman’s form continues to look unorthodox, but he has shown bottom-line improvement with his throws lately. He hasn’t made an error in the past 12 games and has made only three in his last 32 games, dating back to May 17.

“As hard he’s been working with it, it was going to take him at least to the middle of June to where he’d get over the hump with his shoulder,” Johnson said. “I think we’re pretty close.”

While Zimmerman sits tonight against Arizona starter Trevor Cahill, Jayson Werth will return to right field. He left Sunday’s game in the fourth inning with a left groin strain. Werth worked out at Nationals Park yesterday. Johnson planned to give him a day off, but Werth convinced Johnson he could play.

“He said this is something he’s had before, and it’s as bad as he’s had it before, and he’s played through it,” Johnson said. “So he’s in there.”