SANTA CLARA — Thursday was the 49ers players’ scheduled day off. There was no way to gauge their reaction after the team’s morning announcement that it had signed Seneca Wallace to the position of — essentially — the fourth No. 2 quarterback.

But let me take a wild stab at what the players’ reaction was to the Wallace signing: “Huh? Another one?”

No one doubts the motivational skills of 49ers coach Jim Harbaugh. His guys show up every week in the regular season ready to play mentally. Only two of his nine losses as the team’s coach have been by more than 11 points.

Thus, as screwy as it sounded last season when Harbaugh kept saying that Alex Smith was the 49ers’ starting quarterback even though Colin Kaepernick had clearly replaced Smith … well, if that sort of spin kept the locker room in the proper groove for a Super Bowl mission, fair enough.

But this season, there’s a different challenge for Harbaugh in the quarterbacking-attitudinal-spin department. And it will be tougher than last year’s delicate Smith-Kaepernick dance.

Here’s why: By bringing in the 33-year-old Wallace as yet another potential backup, the team and Harbaugh continued their summer camp theme of practically screaming to the world that if Kaepernick gets hurt, the 49ers are doomed.

Now, it’s fine if the rest of us believe that. But the 49er players can’t be permitted to believe that. Otherwise, if Kaepernick does indeed suffer an injury and be sidelined for a few games or even longer, it would provide a ready-made excuse to shrug off a defeat or let intensity slip a bit. And in the NFL, if the intensity slips an inch, it’s the same as it slipping a mile. The margin between winning and losing is too thin.

So, pretend for a moment that you are a 49ers player. And tell me what you’d think if you saw:

1. Kaepernick barely being allowed to break a sweat in the first two exhibition games, then being ordered quickly to the bench because Harbaugh says he doesn’t want anything “freakish” to happen — which means, what, Kaepernick might be supernaturally transformed into a spineless protoplasmic zombie as if he were in a Stephen King novel?

2. Kaepernick being asked in practice to switch from his normal red jersey to a black one, a signal for defenders to not touch him, or create too harsh a breeze while running past him, or criticize his choice of lunchtime salad bar items.

3. No real clarity in the matter of who will be the No. 2 quarterback. Presumptive top backup Colt McCoy has struggled in the first two exhibition games (25.3 passer rating). Presumptive No. 3 Scott Tolzien has failed to raise any eyebrows. A raw rookie, B.J. Daniels, was moderately impressive last week in Kansas City. But he is still, yes, a raw rookie.

4. The curious move of signing Wallace, who, after starting just 21 games in seven NFL seasons with Seattle and Cleveland, couldn’t catch on with any team in 2012 and was recently released by the New Orleans Saints. Is the 49ers quarterbacking roster truly that distressed?

I can imagine what some players must be thinking as they ponder all of the above, even if they won’t talk about it publicly: We must be pretty depth-chart fragile at the most important position on the field. And heaven help us if Kaepernick gets banged up.

That’s not ideal, although it’s not necessarily a disastrous mindset. The Saints players probably feel the same way about Drew Brees. But it surely helped the Saints’ confidence to see Brees on the field last week, looking invincible as he led five scoring drives in the first half against the Raiders.

Kaepernick has not yet had that sort of preseason opportunity. He might Sunday against the Vikings. Or he might not. It would seem to be a good idea for Kaepernick to go out and flex his muscles longer this weekend — and then have one of the four backups look solid and capable. This would send an excellent message to the team and the league. But Harbaugh isn’t tipping his hand about how he will allot playing time. Perhaps he has the Zen of this all figured out in a way that the rest of us can’t comprehend.

For now, the 49er quarterbacking situation behind Kaepernick is a definite issue. The team faces a telling decision. Does it go with Wallace and Daniels, two players whose athletic skills more match Kaepernick’s in terms of running a read-option offense? Or should the nod go to McCoy and Tolzien, more conventional drop-back types?

Whichever way it sorts out, the 49ers would do well to retain Daniels in some capacity. The kid has upside. During a brief discussion with him earlier in training camp, I discovered that before the 49ers picked him in the NFL draft, he interviewed for a job with the F.B.I. after earning his criminology degree at South Florida.

“I always wanted to get into that kind of stuff,” Daniels told me. “As a kid, I watched C.S.I. with my mom every week.”

I predict Daniels will be excellent at dissecting opponents, if he gets a chance.

I just know in these next two weeks before the Sept. 8 opener against Green Bay, the most important thing for the 49ers is to gain more clarity and sureness with their overall quarterbacking mojo. That alone will make this Sunday’s exhibition worth watching.

Contact Mark Purdy at mpurdy@mercurynews.com.