Harbaugh refused to let the cat out of the bag Friday in his last public comments on the budding controversy over two signal callers with hot hands.
Alex Smith has been sidelined since having his bell rung Nov. 11 but was listed as questionable Friday, raising the possibility he could return to the field in place of backup Colin Kaepernick.
"Alex went through his final test today and will be cleared tomorrow, if there are no symptoms," Harbaugh told reporters Friday. "And it's been good. He hasn't had any symptoms since Tuesday."
But, Harbaugh, added, he saw "no competitive advantage" in tipping Niners' fans and the Saints as to which quarterback would get the call.
The San Francisco Chronicle said as a rule Harbaugh refuses to discuss injuries, however indications thus far suggest Kaepernick will get another start while Smith gets additional time to recover.
Sports Illustrated reported this week Harbaugh has told Smith Kaepernick will start Sunday.
Kaepernick, a rookie out of Nevada-Reno, was 16-of-23 passing for 243 yards and two touchdowns Monday in a 32-7 win over Chicago.
The 49ers go into Sunday's game against the Saints with a 7-2-1 record, best in the NFC West.