After Harper got the wind knocked out of him diving for a ball in the ninth inning of Thursday's game against the New York Mets, manager Davey Johnson revealed the 19-year-old phenom has been receiving treatment on his lower back.
Johnson left open the possibility that Harper could miss Friday's series opener against the Red Sox.
"He might not," Johnson told the newspaper. "We'll see how he is on the trip. We'll have to monitor it pretty close."
Harper, who is hitting .276 with five homers in 35 games since being recalled from the minors, was surprised the issue of his back even had been raised and dashed any hope of him not playing.
"I'm totally fine," Harper said. "I'm going to play. I won't be out of the lineup."
Harper occasionally wraps his back with ice after games, but it had not been considered problematic until Johnson broached it Thursday.