(Jacquelyn Martin/AP)

After Harper got the wind knocked out of him diving for a ball, Nationals Manager Davey Johnson revealed that Harper has been receiving treatment from the Nationals’ training staff on his lower back. Asked if Harper would play in Nationals’ series opener Friday at Fenway Park, Johnson left doubts.

“He might not,” Johnson said. “We’ll see how he is on the trip. We’ll have to monitor it pretty close.”

Harper appeared surprised the issue of his back had even been raised and dashed any shot of him not playing.

“I’m totally fine,” Harper said. “I’m going to play. I won’t be out of the lineup.”

Asked when he first hurt his back, Harper replied, “I didn’t hurt it. I’m good. Don’t worry about it. Feel great.”

In the ninth inning this afternoon, Harper dove for a bloop hit along the right field line and missed the ball. After he chased it down and fired the ball back to infield, Harper fell to his knees for a moment. Head athletic trainer Lee Kuntz visited him, but Harper remained in the game.

Harper occasionally wraps his back with ice following games, but it had not been considered problematic until Johnson broached it today.

Since Harper arrived in the majors, he leads the Nationals in batting average (.276), runs (23), hits (37), triples (four) and home runs (five). Even after going 0 for 4 today in a 3-1 loss, Harper has an .859 OPS.

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