WASHINGTON (AP) — Nationals slugger Ryan Zimmerman, hoping to return before the end of the regular season, took on-field batting practice Tuesday for the first time since injuring his right hamstring.

"I need to get back in shape hitting-wise," Zimmerman said before Washington's game against the Atlanta Braves. "I can't take as many swings as I normally do yet. I'm getting fatigued and sore the next day, so that's part of the progression. It's coming along. Everything has been positive and good so far. We're not there yet."

Zimmerman suffered a third-degree strain of his right hamstring strain July 22 in Colorado and had missed 44 games entering Tuesday.

"Running is the biggest thing," he said. "I don't downplay hitting and throwing. It's not a small thing, but running is going to be the biggest test."

Zimmerman said a recent MRI was encouraging. He said he's been able to run at about 50 to 60 percent of full speed.

"I've jogged a couple of times the last few days," he said, "and we really sort of just have to take our time, as frustrating as it is now because we're so close."

The Nationals want a healthy Zimmerman for the playoffs. They began play Tuesday night with an eight-game NL East lead over the Braves.

"I haven't done any side-to-side stuff yet," he said. "Obviously being out here on the field, everybody's going to get excited, including me, and we're going to have to pump the brakes a little bit and make sure when I come back I'm ready to play. Don't want to reinjure it."