ATLANTA — One day after his eyebrow-raising signing of Tim Tebow, Mets general manager Sandy Alderson defended the move in the wake of skepticism about his motives and even some mixed feelings within the clubhouse.

Alderson cited an instance during his time running the Padres in 2007, when he was approached about signing an ex-Marine who had lost part of his non-pitching hand during his second tour in Iraq.

“My answer was ‘why not?’ ” Alderson said Friday, drawing a loose comparison to the novelty of signing Tebow. “Now I don’t put that in the same category as this one, but my response would be the same, which is ‘why not?’ ”

That enthusiasm, however, was not universal. At question: the former quarterback keeping his weekend television gig as a football analyst during an instructional league stint that begins Sept. 18.

Mets rightfielder Jay Bruce said he has little interest in what is sure to become a spectacle.

“What is there, 300 other minor-league guys who are there? Probably more than that? I don’t even know,” Bruce said. “I don’t particularly care. Nothing against or for him. He’s one of them, become a number at this point, you know?”

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Tebow, 29, has not played baseball competitively since his junior year of high school, a span of 11 years. Alderson, however, did not rule out inviting Tebow to major-league spring training.

“He’s an athletic guy,” Bruce said. “Baseball’s a very hard sport. The ball doesn’t lie, so I think everyone else will find out what kind of player he is soon enough.”

Given Tebow’s age, manager Terry Collins said there will be no time for instructional baby steps. But he didn’t dismiss Tebow’s chances of making it to the big leagues.

“There are special people in the world,” Collins said. “I know the statistics probably aren’t in his favor, but who’s to say he can’t make it?”

Alderson reiterated that the signing was his idea and challenged the idea that Tebow will deprive more deserving players of opportunities.

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“There are baseball purists out there who think somebody is going to not get an opportunity because Tim Tebow is playing leftfield or rightfield in Kingsport?” he said. “Give me a break.”

Alderson also repeated his insistence that the move was driven by baseball, not any other factor such as currying favor with an agent (Tebow and Yoenis Cespedes share representation) or marketing.

Said Alderson: “The notion that we’re going to spend $100,000-plus on a player so we can sell a couple of hundred dollars worth of T-shirts in Kingsport, those economics don’t work. This was not about making money.”