In Zimmerman's place, Chad Tracy, activated from the disabled list on Tuesday after missing 55 games with a right adductor strain, started Wednesday's game at third base.
"I'll play [Thursday]," Zimmerman said. "I think I could have played today, but [manager] Davey [Johnson] kind of likes to give us an extra day at this point in the season just to make sure it gets out of there."
Zimmerman was held out of the lineup on Tuesday after appearing to tweak his back while sliding into home during the 11th inning of Sunday's 11-10 win over the Brewers in Milwaukee. The Nats were off on Monday, though Zimmerman's back tightened up enough before Tuesday's game to make Johnson err on the side of caution.
"I feel pretty good about it. He's been getting all kinds of treatment," Johnson said. "I think we have every conceivable person here to lay their hands on it. So he was in a pretty good frame of mind, he was a lot better. It wasn't as sharp as it was the day before. It's still tight."
Zimmerman has also endured lingering soreness in his right shoulder, but after seeing his batting average dip as low as .218 on June 24, the 27-year-old veteran batted .366 with a 1.186 OPS, 10 home runs and 24 RBIs in July.
While Zimmerman was getting another day off, Adam LaRoche returned to the lineup on Wednesday after missing Tuesday's game with back spasms.
"Nobody wants time off, but this month is the hardest of all the months, I guess you could say," Zimmerman said. "Especially with the schedule we've had lately and that we're going to have coming up. We've played 18 [games] in 17 days before the off-day [on Monday] and we're about to play 16 in 15."