Oakland Athletics designated hitter Brent Rooker is set to miss the rest of the season after being diagnosed with a left knee injury that requires surgery. Multiple outlets report that Rooker will undergo season-ending left knee surgery to address a cartilage tear. The procedure is described as surgery to repair the damaged cartilage in his left knee, and as a result he is not expected to return during the current season. Yahoo Sports, Yahoo Sports’ MLB report, Fox Sports, and the Winnipeg Free Press all agree on the basic details: Rooker has a left knee cartilage issue, he will undergo surgery, and the outcome is that he is sidelined for the remainder of the season. While the sources do not provide additional specifics on timing beyond the fact that the surgery is forthcoming, they consistently characterize the injury as requiring operative treatment rather than continued play. Rooker had been one of the Athletics’ key offensive contributors before the injury.