You’d never guess from all the days shooting “Boomtown” on the streets of L.A. that Donnie Wahlberg was anti-Laker.

Growing up in a tough neighborhood outside Boston, Wahlberg was always a diehard Celtics fan. But that ability to keep it close to the vest, to not allow anyone to know what’s really going on inside, is what makes his character, Det. Joel Stevens, so compelling.

“The different thing I did with my acting was keep my emotions available to me more as a human being, and not a caricature of someone,” says Wahlberg. “It was a slow burn the whole season.”

Stevens, partnered with the let-it-all-hang-out Mykelti Williamson’s Fearless, was extraordinarily efficient hunting down the bad guys, but rarely seemed happy about it.

During the first few episodes auds learned his wife was suicidal, but it wasn’t until the season finale that it was revealed their newborn baby had died from a brain aneurysm, and was the cause of their extreme grief.

Wahlberg played nearly every scene with Stevens’ heavy heart in mind.

“There was a risk I took with this character in that the audience could become bored,” Wahlberg explains of Stevens’ melancholy manner. “The danger in playing it down is that the writer (Graham Yost), halfway through the season, could change direction. … I think as the year evolved, though, Graham found ways to use the original concept.”

“Boomtown” is Wahlberg’s first entry in primetime television as a series regular, but he’s no stranger to celebrity.

As a member of ’80s boy band New Kids on the Block, he was showered with compliments from teenage girls.

But TV critics — who are widely singing his praises — are a much stodgier bunch and don’t blow kisses. In tune with his low-key character, Wahlberg’s a bit embarrassed by all the kind words for both his work and the show.

“At some point you figure this many people can’t be lying.”