Change will accompany Danny Regan (Donnie Wahlberg) to Massachusetts when he begins his own “Blue Bloods” spin-off, “Boston Blue” — and not because he’ll be a fish out of water in a new town. His son, Sean, will be a big part of the show — but the character won’t be played by his longtime portrayer, Andrew Terraciano . Instead, the actor has been replaced by Mika Amonsen of “Thanksgiving” fame for the new program. Since Sean has become a beat cop since viewers last saw him, producers reportedly wanted the character to have a new look that fits in with this new profession.

Sean’s job has apparently put him in a New England mood. Aware of the stellar policing legacy his family’s established in New York City, Sean has moved to Boston to get a start on the force far away from the generational pressure inherent in being a Reagan with a badge. Unfortunately for him, Danny soon moves to Boston too and takes a job with the cops, making the father and son colleagues just like Danny was with his brothers and dad. This adds a crucial element to “Boston Blue” that was missing at first blush — a strong family connection between Danny and other members of the cast. After all, the Reagans’ tightly knit bonds made “Blue Bloods” stand out compared to other procedurals and gave the drama many of its big narrative hooks.

While this will allow Sean and Danny to commiserate just like their family would during the Reagans’ famous shared dinners on the mothership show, it’ll also provide obvious tension between the dad-and-son duo. It will be Sean’s job to step out of Danny’s shadow, for better or for worse, while Danny will have to learn to let go of his rookie son. But while this might make for great plot fuel for “Boston Blue,” it’s a storyline choice that doesn’t make a whole lot of sense for the Sean fans knew back on “Blue Bloods.”

For longtime fans, Sean becoming a beat cop is an odd choice for the character. During his time on “Blue Bloods,” Sean never seemed interested in law enforcement as a career choice — he instead expressed his love of art and a desire to become a firefighter. While he obviously loves and respects his family, when compared to his more staid and responsible brother Jack (Tony Terraciano), Sean is a rebel. Over the course of the series, Sean even runs afoul of the law multiple times for a variety of youthful mistakes, like skipping class, failing to study, and underage drinking. Ergo, making him a police officer like much of the rest of his family feels like an unexpected and disappointingly boring plot twist. 

Naturally, a son with a brand-new face won’t be the only challenge Danny Reagan will be forced to endure in Beantown. He’ll likely experience some pushback from his new partner, Detective Lena Silver (Sonequa Martin-Green), a cop who has her own long family history of upholding the law. He’ll also meet other members of the Silver family while working in Boston: Sarah (Maggie Lawson), Jonah (Marcus Scribner), and Mae (Gloria Reuben). Ernie Hudson will also appear as Reverend Peters when “Boston Blue” debuts on CBS in the fall.