Rendon, who went 0-for-4 with an RBI sacrifice fly, missed 25 games with a strained left quadriceps. In six games on a rehab assignment with Class A Potomac, he went 8 for 17 with three walks.
"I feel like I'm swinging the bat well and have my timing at the plate, which is what I wanted to accomplish down there," Rendon said. "I feel good."
The Nationals, who have a three-game lead over the New York Mets in the NL East, optioned rookie right-hander Abel de los Santos to Double-A Harrisburg. He made two relief appearances and allowed one run in 1 2/3 innings.
Two other Nationals starters are also on rehab assignments, left fielder Jayson Werth (fractured left wrist) at Triple-A Syracuse and first baseman Ryan Zimmerman (plantar fasciitis in left foot) at Double-A Harrisburg.
Nationals manager Matt Williams said both are close to being activated.