Harper aggravated his sore left knee three times in Sunday’s 6-1 win over the Philadelphia Phillies, twice with head-first slides in the first inning.
For good measure, he then fouled a pitch off the knee in the third inning. He was limping throughout the game and was removed for a pinch runner after drawing a walk in the seventh.
Johnson also announced that left-hander Ross Detwiler will miss a second start and go on the 15-day disabled list because of a strained oblique muscle.
Source: ESPN.com