Sveum said that infielder Jeff Baker was unavailable on Saturday after coming down with the same flu virus that has sidelined Garza.
"He's almost getting sicker," Sveum said. "He's not getting better, that's for sure."
Sveum said that backup catcher Welington Castillo will probably start Sunday's series finale, giving Geovany Soto a day off.
Despite pitching four of the last five days, Dolis would "probably be OK" to pitch on Saturday if called upon, Sveum said.
The Cubs entered Saturday with at least 10 hits in each of their last three games, their longest stretch since a four-game streak from Aug. 12-15, 2011.