Rendon played in three minor league games at Double-A Harrisburg during the past 10 days while rehabbing from a sprained MCL in his left knee, but has been out since Saturday after he couldn't get loose and was scratched from the lineup.
"We're gonna have to slow his progress down a little bit," Nationals manager Matt Williams told reporters. "He's felt it for the last couple days, so we're going to have to sit him a little bit longer and make sure it's OK before he resumes activity. It's just not getting loose for him."
Williams would not give a timetable for Rendon's return, but pointed out that Nats infielder Yunel Escobar had the same injury during spring training and had to sit out 10 days without baseball activity.
Rendon, who is working at third base and second base at Harrisburg in preparation to play both positions with the Nationals, was evaluated by team doctor Dr. Wiemi Douoguih on Monday in Washington.
The Nationals originally had hoped that Rendon, who finished fifth in the National League MVP voting last season after hitting .287 with 21 home runs and 83 RBIs, would be able to return by late this week.