SAN FRANCISCO -- As if there were any doubts, Alex Smith is the 49ers' starting quarterback heading into the regular season.
Coach Jim Harbaugh formally made the announcement after San Francisco's 20-17 victory at San Diego in Thursday night's preseason finale.
"I'm pretty sure we can say that," Harbaugh said. "He played with a very cool head and made good decisions. He played the way you want him to out there -- calm, cool, collected."
Smith went 8 for 10 for 45 and wasn't sacked.
Harbaugh had said all along the No. 1 job was Smith's to lose, and the new coach appreciated his QB's leadership and initiative leading workouts at nearby San Jose State during the lockout this summer in what was deemed "Camp Alex."
Smith, the 2005 No. 1 overall draft pick out of Utah, took the majority of reps with the first-team offense during training camp, too. Now, he will be the guy going into the team's Sept. 11 opener against the defending NFC West champion Seattle Seahawks at Candlestick Park. Smith returned to the Niners for 2011 on a $5 million, one-year deal after a positive meeting with Harbaugh -- an ex-NFL quarterback himself -- during the spring.
While Smith didn't throw a touchdown pass in his four preseason starts, Harbaugh has long believed he can succeed in the first-year coach's West Coast offense despite his up-and-down tenure with this franchise.
Smith was slightly behind after missing the initial six practices of training camp per the new labor rules for when free agents could start workouts. He treated each day as a competition to win the job, never assuming anything.
Rookie second-round pick Colin Kaepernick had competed for the job. Kaepernick threw two more interceptions Thursday night, giving him five during the team's 2-2 preseason.
The 27-year-old Smith threw for 2,370 yards and 14 touchdowns in 11 games and 10 starts last season, but he also threw 10 interceptions and was sacked 25 times. He shared the starting role with Troy Smith, who is no longer with the team.
Smith's return to the 49ers as a free agent surprised many. He wasn't expected to be back when last season ended with a 6-10 record and an eighth straight year out of the playoffs and without a winning record.
Smith said Thursday he hadn't allowed himself to think too far ahead, especially after the bad taste he had from a 30-7 home loss to the Texans last Saturday.
"To be honest, I know it's coming up, but after the Houston game, I wanted to focus on this game," Smith said in San Diego.