Gorzelanny (7-8, 3.90 ERA) has been sidelined after taking a line drive off his left hand on Sept. 1.
Silva (10-6, 4.22 ERA) has not pitched since Sept. 7. He was scratched from his last scheduled start Sept. 13 because of a right shoulder strain.
"We'll have to see how quickly [Silva] comes back," Cubs manager Mike Quade said.
The Cubs' rotation for the final home series against the Cardinals will be Gorzelanny on Friday, Casey Coleman (2-2, 5.02 ERA) on Saturday and Jeff Samardzija (2-1, 6.00 ERA) on Sunday.