Oakland activated switch-pitcher Pat Venditte from the disabled list and optioned him to Triple-A Nashville to make room for Valencia on the 25-man roster. They did not need to make a 40-man move for Valencia.
The 30-year-old Valencia has played both infield and outfield throughout his career, but played mostly left field with the Jays in 2015. When Ben Revere arrived from the Phillies via trade, Valencia was the odd man out and was designated for assignment.
The Athletics did not need to make a trade for Valencia because he was outrighted to the minor leagues and off the 40-man roster. Valencia, considering how well he's hit, did not even pass through, which does not happen all the time.
On the season, Valencia is hitting .296/.331/.506 with seven home runs and 29 RBIs over 173 plate appearances.