OAKLAND -- The Oakland A's today announced that they have released infielder Todd Walker. Walker was designated for assignment on May 12 when the A's recalled Dallas Braden. He was on the A's Opening Day roster and hit .271 with no home runs and four RBI in 18 games. Walker started nine games at first base for the A's while Dan Johnson was on the disabled list. He was signed by the A's to a Minor League contract on March 30 after being released by San Diego.