"[Zimmerman] did a full workout, so he ran light bases, he took grounders, he did a full batting practice," said Nationals manager Matt Williams. "He'll do that again tomorrow and we'll see where we can go from there, how we can progress.
"He feels good, but it's still controlled. He hasn't hit a ground ball to short and had to run full speed to first yet ... that's a telling sign."
There was no timetable set for either player's return, but Williams seemed happy with the rehab progression each player has seen so far.
Zimmerman and Rendon's return to full health will help a Nationals offense that has scored 336 runs this season (seventh in the National League). Before hitting the disabled list on June 25, Rendon was hitting .290 with a .737 OPS. Zimmerman was batting just .209 in 56 games, but is a career .282 hitter with an .818 OPS.
Williams also talked briefly about the progress of relief pitcher Aaron Barrett (right biceps strain) and outfielder Jayson Werth (left wrist fracture).
"Barrett threw a bullpen [today]," Williams said. "He's scheduled for tomorrow's game [with Potomac]. Scheduled to start it, throw one inning and get back to competition.
"And Jason's healing up. Continuing to heal that bone, so as soon as that bone is fully ready to go, he'll be ready to go."
Barrett had posted a 5.06 ERA in 21 1/3 innings so far in 2015 before getting injured, but his 2.21 FIP suggests that he was a bit unlucky. Werth has played in just 27 games this season and was hitting .208 before hitting the DL on May 28. Werth isn't expected to be back until at least August.
Carlos Collazo is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.