Kubel batted just .159 last month and through 10 games this month, he is hitting .154 with only five RBIs.
"Kubel has been struggling a little bit lately," Gibson said. "Want to play some new guys. We haven't manufactured runs, so it's a little different group today."
In his spot, Gerardo Parra received the start Sunday in left field against the Giants and Ryan Vogelsong.
When Kubel does return to the lineup, Gibson is considering moving him down in the order from his typical three-through-five spot.
"It's possible. He didn't have a good August; he hasn't driven the ball like he has," Gibson said. "It's late in the year and it's not as easy as it looks."