Rivas went 2-for-4 with a triple and a run scored in Saturday's loss to the Giants.
Rivas, who was recalled from Triple-A Iowa at the end of August, has been seeing regular playing time at first base recently. Saturday marked his fifth start there over the last six games, and he responded with his second triple of the season. Rivas may sit against lefties moving forward, though it looks like he'll play regularly against righties.