The third baseman hasn't played since Friday night, when he took a Carlos Quentin grounder off his right hand, forcing his removal from the game. X-rays showed no fracture, but the hand has been swollen and tender.
Rendon swung in the cage yesterday, but still reported some soreness, especially around the thumb area. That put off his return at least one more day and led to today's try with the bat.
"It's a little bit sore still," said Nationals manager Matt Williams. "He hit today - he's a lot better today than he was yesterday. I think one more day. He'll be ready to go tomorrow."
Williams said Rendon was available tonight as a pinch-hitter.
Once again tonight, Kevin Frandsen will play third base and hit second.