SANTA CLARA -- Jim Harbaugh used a version of the word "responsibility" eight times in 15 minutes Monday, and there were some strong conscious and subconscious reasons for this.

The 49ers are Harbaugh's responsibility, every speck and milligram. They play his style, they've taken on his character, they will go as far as he takes them.

And Harbaugh's gut-instinct decision to play Colin Kaepernick over veteran Alex Smith has changed the entire feel and scope of the season.

Everything turned when Harbaugh made the quarterback switch, and the result is very much yet to be determined.

Harbaugh surely had an inkling of this when he made the big switch over the last few weeks. He's neither blind nor deaf: He understands all the angles here.

But I think over the last few days, the full and potentially errant consequences truly began to hit home.

Maybe, as suggested by Kaepernick's first two starts, the QB change will push the 49ers to a title in February.

If so, Harbaugh's a genius.

And maybe, with such an inexperienced QB, there will be too many more stumbles like Sunday's error-strewn loss in St. Louis.

If that's how it plays out, Harbaugh's wild gamble could cost the franchise its best shot at a Super Bowl in decades.

Which all circles back to this: Harbaugh didn't have to switch QBs, but he did it, anyway.

The 49ers lost Sunday, and Harbaugh rightfully said Monday that it wasn't at all Kaepernick's fault.

In fact, Harbaugh praised Kaepernick's overall performance against the Rams and reiterated that Kaepernick remains the 49ers' starter.

The risky play-call that produced a gigantic Kaepernick error and Rams touchdown was on Harbaugh and his staff; the entire season is on Harbaugh, and he shouldn't and wouldn't want it any other way.

"Responsibility-taking starts with me on that option play that resulted in the nightmare scenario," Harbaugh said of the fourth-quarter exotic pitch play.

"And it's a position in the game where I should not let that play be called. So I take responsibility for that."

But Harbaugh has backed himself into a little bit of a corner here with the QB decision -- really, the first little sticky point of his two-season 49ers tenure.

He has said it's about going with the "hot hand" and that this wasn't a QB controversy since both guys have been playing so effectively.

That was Harbaugh's way of denying that he had Kaepernick penciled in all along, and it also allowed him to insist that he still supports Smith.

But if you say it's about going with the hot hand, what happens when and if Kaepernick cools off?

What happens if defenses sit back in a deep zone -- as St. Louis did -- and dare Kaepernick to stay patient and make the short throws all game long?

If Harbaugh is true to his words, shouldn't he seriously consider putting Smith back out there at some point?

Monday, I asked Harbaugh directly if Smith could win the starting job back. And even though Harbaugh said that he could, just listen to the indirect way he said it.

"Alex is not out of this," Harbaugh said. "He's won us a lot of football games.

"He's preparing himself to play in each of these games every single week. That's what his mindset has to be, as if he was the starting quarterback."

In truth, Harbaugh has committed to Kaepernick in every way but by official pronouncement. You don't make this switch under these circumstances unless you're sure about Kaepernick.

And again, Harbaugh and his staff might be absolutely right about Kaepernick.

No doubt, he throws the deep ball beautifully, and, even in defeat, he broke off that breathtaking 50-yard fourth-quarter run.

"Thought he responded (after the misplays) with some big throws and some big plays," Harbaugh said.

But Smith made a lot of big throws and starred in a lot of big 49ers victories, too. Including a playoff victory not too long ago. And yet Smith's the one on the sideline now, while Kaepernick is at QB.

On Monday, Harbaugh insisted the move wasn't made just to get Kaepernick ready for January; it was made to win every game.

So far, the 49ers are 2-1 with Kaepernick at the helm, with an easy home game against Miami on Sunday and then two rough road games -- at New England and at Seattle.

Kaepernick almost certainly will be the QB for all of those games, as the 49ers vie for NFC playoff positioning ... and to stay ahead of the Seahawks in the NFC West.

It's up to Harbaugh to make sure Kaepernick is ready for this; it's Harbaugh's responsibility to make sure his risky decision doesn't scramble up the season.

It's all tied to one position, one decision, and the coach who is responsible for it all.

Read Tim Kawakami's Talking Points blog at blogs.mercurynews.com/kawakami. Contact him at tkawakami@mercurynews.com.