ATLANTA - The Cardinals placed infielder Brendan Ryan on the 15-day disabled list Thursday and promoted 2005 first-round draftee Tyler Greene to fill a growing void at shortstop.

Manager Tony La Russa acknowledged following Wednesday’s 5-3 win over the Atlanta Braves that a roster move was necessary since starting shortstop Khalil Greene will be unavailable for at least the first two games of the 4-game series against the Washington Nationals. Greene is suffering from a right forearm strain that makes it difficult for him to throw.

Ryan pulled up after running out a fifth-inning ground ball. He left the game and was diagnosed with a mild hamstring strain. La Russa said he would be out a minimum “5-7 days.” Given Khalil Greene’s condition, a move had to be made.

Tyler Greene is hitting .296 at Triple-A Memphis. Drafted as a college junior at Georgia Tech two picks behind Colby Rasmus, Greene also has contributed nine RBI and seven stolen bases in 71 at-bats. His 17 strikeouts are partly offset by a .412 on-base percentage. Greene fared well in spring training after being placed on the 40-man roster last November. He likely will become the Cardinals’ starting shortstop until Khalil Greene improves. A Texas League (AA) All-Star last summer, Tyler Greene, 25, arrives after taking only 182 at-bats total at Triple-A.