Zimmerman had been on the disabled list since April 18 with a left hamstring strain. He missed 14 games.
His rehab stint was a short one. Zimmerman appeared in just one game with high-A Potomac, getting three at-bats and going 0-for-3. That's apparently all he needed before feeling he was ready to return.
Zimmerman is hitting .225 with two doubles, a triple, one home run and 11 RBIs this season.
Rendon batted .240 in eight big league games, picking up six hits during his brief stint with the Nats. His on-base percentage was an impressive .367 and he went 2-for-3 with a walk in his final game with the Nats for the time being.
Here are the 22-year-old's thoughts on his first stint in the major leagues.