Sappelt, who batted leadoff on Tuesday for the first time this season, is trying to impress on the Cubs that he could handle the role that Johnson filled, which was providing a right-handed bat off the bench plus someone who could sub in the outfield.
Sappelt started things out well against the Rockies, hitting his first Major League home run in the first inning.
"Since he's been here, he's shown us some really good at-bats and shown the ability to hit a fastball and get his walks as well," Cubs manager Dale Sveum said before Tuesday's matchup against Rockies lefty Jorge De La Rosa. "I thought I'd stick him in that leadoff spot and see what happens."
Sappelt was hitting .333 against left-handed pitchers in 18 at-bats since he was called up from Triple-A Iowa on Sept. 1. At Iowa, Sappelt batted .331 against left-handers and .236 against right-handed pitching. He primarily batted second and seventh with Iowa.
"The guy's got some hitting ability," Sveum said. "He's got bat speed, he can hit a fastball. That's ahead of the scale right there to be able to do that, especially doing it off the bench when you're going to face velocity and stuff."
Johnson opened the year with the Cubs but was dealt at the Trade Deadline to the Braves.