Luckily, the organization is calling the injury a lower leg bruise. Harper, who left the game after being hit by Greensboro's Jheyson Manzueta, will be re-evaluated Monday morning.
Nationals third baseman Ryan Zimmerman, who was playing a rehab game Sunday in Hagerstown, said Harper's injury does not appear to be severe.
"He'll be all right, I think it's more precautionary," said Zimmerman of Harper being taking out of the game.
Lerner echoed Zimmerman's reaction.
"I'm sure he was seeing stars, but I think he'll be fine," Lerner said.
After being hit, the 18-year old immediately dropped his bat and sat in the batter's box holding his legs, which were stretched in front of him. When the Suns' trainer came over, Harper initially had difficulty standing up, but did so with assistance and hobbled off the field.
Harper, who is batting .338 with 13 home runs and 41 RBIs in his first year in the Minors for the Nationals, was not made available for comment.
Avi Zaleon is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.