Here’s what we know about why the recast happened and how everyone involved feels about it.
A new chapter for Danny and Sean
Boston Blue follows Danny Reagan, played by Donnie Wahlberg, as he leaves New York for Boston. This time, the story flips the dynamic fans are used to: Danny is now the father of a fellow police officer. Sean has joined the Boston Police Department, and the series kicks off with him seriously injured during a building fire.
Co-showrunner Brandon Margolis explained that this shift in story direction drove the recasting decision. Speaking to Variety, Margolis said the team loved Terraciano’s work on Blue Bloods but felt the spinoff needed a different energy.
According to Margolis, both Sean and Danny are entering completely new territory. Danny has never been the father of a cop before, and Sean is turning over a new leaf as a young officer trying to prove himself. The creators felt that bringing in a new performance helped underline that change. While the character and his relationship with Danny remain the same, Margolis said the dynamic is intentionally different.
Andrew Terraciano’s reaction
Terraciano learned about the recasting on a very emotional day — the day he graduated from college in May 2025. In an interview with Us Weekly, he shared that his family was informed producers might be looking for a different direction for Sean.
Terraciano also revealed that Wahlberg personally called him soon after. He described the conversation as a meaningful moment with someone he considers both a friend and a mentor. Looking back on his time on Blue Bloods, Terraciano said he’s grateful for every moment he spent playing Sean and will always treasure the experience.
Importantly, he made it clear there’s no bitterness. He said the role doesn’t belong to just one person forever and believes someone else can do something special with the character.
Mika Amonsen steps in
For Mika Amonsen, taking over a long-established role came with pressure. He admitted to Us Weekly that some fans reacted negatively at first, which he understands. Still, he said many viewers are enjoying where the show is headed and how Sean’s story is developing.
Amonsen said he worked hard to honor both the character fans love and Terraciano’s original portrayal, while also making the role his own. He was cast quickly and had to jump in fast, studying Blue Bloods to understand Sean’s growth and his bond with Danny by the end of the series.
The early days, he admitted, were stressful. He felt a strong responsibility to respect Terraciano and the legacy of the character, especially given how long fans had watched Sean grow up on screen.
Moving forward
Despite the initial shock, the message from everyone involved has been consistent: this is still Sean Reagan, just at a different stage of life. Boston Blue is about change — for Danny, for Sean, and for the world they now operate in.
Boston Blue airs Fridays on CBS, with new episodes streaming the next day on Paramount+.
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