Harper was scratched due to left knee soreness. He had originally been scheduled to start in right field and was replaced in the lineup by Clint Robinson.
In 2013, Harper underwent surgery on his left knee to repair a bursa sac.
The 22-year-old Harper currently leads the National League in home runs (29), runs (77), on-base percentage (.460), slugging percentage (.650) and OPS (1.110). He is hitting .333 with 69 RBIs in 105 games.
The Nationals (58–53) enter Tuesday one and a half games behind the New York Mets for first place in the NL East.
- Molly Geary