SANTA CLARA — When does Jim Harbaugh ever volunteer specific information about acquiring a new player?

Just about never. Harbaugh almost never does, not intentionally.

So it was interesting Monday when Harbaugh gave a detailed answer about replacing fullback Bruce Miller, out with a broken scapula.

“We’re bringing in Owen Marecic, hopefully in route, and we’ll look at our options,” Harbaugh said of his former Stanford fullback/linebacker.

And then … the 49ers didn’t bring in Marecic and instead examined other fullback avenues.

What happened here?

Here’s what: Though far from a franchise-turning moment, these machinations partly illuminated the creative tension that fuels Harbaugh’s relationship with general manager Trent Baalke.

Harbaugh wanted Marecic, surely with the knowledge that Baalke and the personnel department had reservations in the past.

Though a source stressed Tuesday night that Baalke was on board with re-signing Marecic and that Marecic himself was the one who chose not to come, it was an interesting time for Harbaugh to volunteer a name.

There is a back story, there are discussions, and relationships can evolve. And tension between a strong coach and confident executive, by the way, is not necessarily a bad thing at all.

Sometimes it’s the best way for two leaders to coexist — the New York Giants won Super Bowls with Bill Parcells and George Young alternately clashing and embracing.

Bill Walsh had his moments with Eddie DeBartolo, Jr., and John McVay, and that all turned out relatively well.

So it was notable that Harbaugh offered Marecic’s name so easily not long after Marecic’s brief, inactive stint with the team this season.

Important point: Harbaugh doesn’t have control over who gets signed — he has a great deal of influence, but he’s not in charge of the 49ers’ roster.

That contracted power belongs to Baalke, and it’s the way CEO Jed York wants it. (And Harbaugh, I’m told, never asked for it during the January 2011 negotiations to join the 49ers.)

And yes, when Harbaugh sits down with York to talk about a new contract this offseason, I would guess that he will ask for more input in such personnel matters.

No doubt, Baalke should and probably does seek Harbaugh’s opinion, mostly relating to the 49ers offense and especially the quarterback position.

Baalke and Harbaugh have agreed on many things since January 2011, and they have built this 49ers team into a model franchise that is bristling with talent.

But from what many sources have told me, there certainly have been disagreements, including over …

Marecic: Harbaugh wanted to draft him in 2011 and was not pleased when Baalke skipped him, taking, among others, Kendall Hunter nine picks ahead of Marecic in the fourth round.

The third-string QB merry-go-’round this season: Harbaugh got a little manic going from Scott Tolzien to B.J. Daniels to Seneca Wallace to John Skelton to McLeod Bethel-Thompson … Until the front office finally urged Harbaugh to settle it down. Bethel-Thompson is currently on the practice squad.

Harbaugh has offered strong public suggestions that the 49ers should give new deals to several players, including safety Dashon Goldson last season, that Baalke probably never planned to give. On Monday, Harbaugh said the same about kicker Phil Dawson and safety Donte Whitner. “Pay the man,” Harbaugh said of Dawson. Gee, who was Harbaugh talking to?

According to multiple sources, Baalke and York believed linebacker Aldon Smith would play sparingly when they agreed to keep him on the active roster for the Indianapolis game two days after his DUI arrest. Then Smith played all 72 defensive snaps in the loss to the Colts before entering a rehab center a few days later.