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.
"But I thought across the board, offensively, everybody stepped it up, and we did a better job, and I was happy to see that. We've still got to keep getting better. We've still a lot of improvement to make."
Gabbert ended a personal 10-game losing streak as a starter and broke the Niners' nine-quarter touchdown-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 for a passer rating of 76.2. It was his fourth straight start with at least two interceptions.
Gabbert was not sacked, though, and he gave the 32nd-ranked offense in the NFL a spark. Kaepernick had been sacked 28 times in his past eight games.
"I'm so appreciative for this opportunity," Gabbert said after winning his first start since Week 3 of the 2012 season with the Jacksonville Jaguars, who drafted him No. 10 overall in 2011. "I just wanted to go out there ... and just have fun. You play well when you having fun, and that was the biggest thing."
Kaepernick, meanwhile, has had anything but good times against the Seahawks. He is 1-6 against Seattle in his career, including playoffs, with three touchdowns and nine interceptions while completing just 53.4 percent of his passes. His Total QBR of 21.1 against the Seahawks is his lowest against any opponent he has faced more than once, according to ESPN Stats & Info.
The Niners have lost four straight games to Seattle by a combined score of 79-30. Gabbert has not faced the Seahawks in his career.
"All I know is we got the victory today," Gabbert said Sunday. "We got a bye week coming up, and we're going to prepare for Seattle. That's our next game up there. So whatever 11 guys we march out on the field, we're going to go up there and expect a victory."