Manager Matt Williams confirmed the diagnosis after the Nationals’ 5-3 loss to the Rays.
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Harper threw the ball in from right field in the sixth inning before he dropped to the turf writhing in pain and holding his left leg. He was able to walk off the field without any assistance.
Harper is having the best season of his four-year career with a .344 batting average, 22 home runs and 52 RBIs in 64 games.
