The Colorado Rockies announced that left-handed pitcher Tyler Anderson will have arthroscopic surgery on his left knee Friday and is expected to miss as many as four weeks.
Anderson was placed on the disabled list Monday after leaving Sunday's start after 2⅓ innings with what was called at the time a left hamstring cramp.
Anderson previously missed 3½ weeks this season with left knee inflammation and pitched Sunday while wearing a brace over his left knee.