SANTA CLARA, Calif. » Colin Kaepernick has earned himself a third straight start at quarterback for the San Francisco 49ers.

Coach Jim Harbaugh made the announcement today that Kaepernick would go Sunday at St. Louis over Alex Smith after the second-year pro led the NFC West-leading Niners (8-2-1) to victories in the past two games, his first two NFL starts.

“The rationale is we have two quarterbacks that we feel great about as a starting quarterback,” Harbaugh said. “Both have earned it, both deserve it — Alex over a long period of time, Colin by virtue of the last three games. It tips the scales. Colin we believe has the hot hand. We’ll go with Colin. And we’ll go with Alex. They’re both our guys.”

Yes, Harbaugh is still leaving open every possibility, saying it still could be a week-to-week decision. All Kaepernick knows is he will begin Sunday’s game under center.

Harbaugh warned, “I wouldn’t assume anything.”

“To start talking about speculation or every permutation you could get into, we’re not going to speculate on it,” Harbaugh said. “We’re worried about everything and we fear nothing.”

The reigning NFL Coach of the Year told his players on the field at some point during this morning’s walk-through practice.

Kaepernick has completed 48 of 74 passes for 680 yards and three touchdowns with one interception and was sacked six times. He has a 102.3 passer rating.

“I don’t know if it’s a hot hand. Whatever you want to call it. I’m just happy I get to go back out there,” Kaepernick said. “It’s a great chance to lead this team and show we’re a great team and we can go into the playoffs.”

Smith, the 2005 No. 1 overall draft pick, hardly looked happy on the sideline during Sunday’s win over the Saints after being medically cleared from a concussion suffered in the first half of a 24-24 tie against St. Louis on Nov. 11.

As the questions about his quarterback decision kept coming from every direction, Harbaugh repeatedly said, “I think I’ve covered and plowed that ground about as thoroughly as it can be plowed.”

He did say kicker David Akers is nursing an undisclosed injury, and that’s why the 49ers worked out kickers Tuesday.

“David Akers is working through something and we want to make sure we have a Plan B,” Harbaugh said.