Valera has a .303 career batting average in 800 minor league games over eight years with the Cardinals organization. The 26-year-old utility player has spent the majority of his career at second base, but has seen time at shortstop, third base and all three outfield positions.
Last year, Valera made his big league debut as a September call-up, going 1 fo 10 with one walk in five games. He spent most of the season with Triple-A Memphis. Last winter, he played in Venezuela, where he was chosen the league's most valuable player.
Valera was originally signed as a non-drafted free agent by the Cardinals in 2010.
Mieses hit .247 in 411 career minor league games over five years with the Dodgers organization.
Sunday's deal fully restores the Dodgers' 40-man roster.