The Cardinals have called up second baseman Kolten Wong, one of their top prospects, from Memphis and he will join the team for Friday's game in Chicago.
The Cardinals will send outfielder Adron Chambers down to Memphis.
Wong, the team's first-round pick in the 2011 draft, will wear No. 16.
Wong, a lefthanded hitter, was expected to be a September call up for the Cardinals, but he will be arriving two weeks early.
He was hitting .303 in Memphis with 10 home runs, eight triples and 21 doubles. In his last 10 games at Memphis, he was hitting .351.
The 22-year-old from Hawaii is in his third professional season. He hit .287 last season at Class AA Springfield in 2012.
Why the move was made now is not clear. Third baseman David Freese came out of Thursday's game in the eighth inning and was replaced by Daniel Descalso, but there was no announcement of an injury. Wong doesn't figure to be playing anywhere besides second base, where Matt Carpenter is firmly planted. But Carpenter can also play other positions, giving the Cardinals some options to get Wong in the lineup. Wong did not play for Memphis on Thursday.
Asked before the game if Wong would be called up in September, general manager John Mozeliak said, "I'm not going to speculate on what the September roster will look like." Asked, with reference to Wong, if he saw a candidate or need to change the look of the team offensively, Mozeliak said, "Not really."