Jansen is unavailable for Saturday's game against the Diamondbacks due to a back injury, David O'Brien of The Athletic reports.
Jansen felt a twinge in his back during Friday's relief appearance, and he'll rest for at least one game. However, his injury isn't considered significant, so he should be considered day-to-day. If Atlanta encounters a save situation Saturday, A.J. Minter and Will Smith will likely be the top options to fill in as the closer.