Pena was pulled from Saturday's contest against Seattle due to right posterior knee tightness, Brian McTaggart of MLB.com reports.
Pena got two plate appearances in the contest, going 1-for-3. Following his single in the fourth inning, he advanced to second on a flyout and to third on an Isaac Paredes single. Following the Paredes hit, Pena exited and was replaced by pinch runner Nick Allen, who subsequently took over at shortstop. The severity of the injury isn't clear, and Pena should be considered day-to-day for the time being.