The Reds placed Greene on the 15-day injured list Saturday due to right elbow soreness.
Greene has been one of the National League's best pitchers this season, recording a 2.83 ERA, 1.02 WHIP and 162:53 K:BB across 143.1 innings. For the first time this season, Greene will be forced to the IL after experiencing pain in the elbow of his throwing arm following his start Tuesday versus the Cardinals. If the 24-year-old can return after the minimum 15 days, he would miss only miss two starts. However, the Reds could choose to play it safe with their ace, even with the team being only four games out of a wild-card spot. A corresponding move wasn't immediately announced, and it's unclear who'll take Greene's spot in the rotation Monday and beyond.