On Tuesday, Zimmerman took about 40 "dry swings" -- swinging the bat by himself with no baseball -- in the batting cage, and Wednesday, he was back to doing the same thing. The 23-year-old, bothered by a small labral tear in his left shoulder, says he will eventually progress to hitting off a tee and then getting soft tosses, but doesn't know when that will be.

Still, just the mere fact of swinging a bat is progress for Zimmerman, who's been out for about a month but is starting to see the effects of his rehabilitation program.

"It's feeling better," Zimmerman said before heading out to the cages for the second straight day on Wednesday. "It's getting stronger, but it's hard to notice anything [in the early stages of rehab]."

His cuts on Tuesday were the first time he had picked up a bat since an unsuccessful attempt to take part in batting practice in a series against the Diamondbacks in late May. Zimmerman said season-ending surgery "is always a possibility, but I'm hopeful that we won't need to do it."

Although there is still no timetable for his return and no telling whether he will keep proceeding to eventually play in rehab games or go under the knife for the rest of the season, Nationals manager Manny Acta said he sees progress.

"It's encouraging," Acta said before the series finale against the Marlins at Dolphin Stadium. "We get happier and happier every time we see him do more and more and getting toward that final goal, which will be to add him to our team."

In other injury news, Acta said outfielder Austin Kearns, who's been rehabbing in Triple-A Columbus from loose bodies in his right elbow, is expected to join the big league club Thursday in the series opener against the Reds.

"Up to now, that's the plan," Acta said. "[Having Kearns] improves [the defense] big time. ... We don't have to have that carousel that we've been having out there of having three or four different guys."

Acta said Kearns would start in right field and Elijah Dukes would move over to left when the 28-year-old gets back. Roger Bernadina would likely remain in center field until Lastings Milledge returns from a right groin injury.