The Niners, who improved to 3-6 with a 17-16 victory over the Atlanta Falcons at Levi's Stadium on Sunday with Gabbert under center, are on their bye week and next play at the Seattle Seahawks on Nov. 22.
Earlier in the day, in his weekly media conference, coach Jim Tomsula said he was not going to make the announcement until after staff meetings and meeting with the quarterbacks.
"Blaine did a nice job, did some really good things with his feet and his arm and his brain," Tomsula said at the time. "Really did a nice job, so congratulations to him."
Gabbert broke the Niners' nine-quarter TD-less streak with a pair of touchdown passes to tight end Garrett Celek in the second quarter. He threw for 185 yards on 15 of 25 passing with the two touchdowns and two interceptions, his fourth straight start with at least two INTs, for a passer rating of 76.2. Gabbert was not sacked, though, as as he gave the 32nd-ranked offense in the NFL a spark, while Kaepernick had been sacked 28 times in his past eight games. He's going to be a risky fantasy option going against the Seahawk defense on the road.