Pennington was released by the Athletics on Saturday, Susan Slusser of the San Francisco Chronicle reports.
The 34-year-old has received at least some big-league playing time in 11 straight seasons, but he hasn't recorded an above-average batting line since 2009 and has posted a wRC+ above 75 just once in the last seven seasons. He could still stick somewhere as organizational depth this season but is unlikely to make a significant impact.