If you watched the highly anticipated Boston Blue premiere on CBS last week, you may have noticed something familiar
yet different. One character carried over from Blue Bloods didn’t quite look the same.
In a move that surprised longtime fans, Mika Amonsen has taken over the role of Sean Reagan, the youngest son of Danny Reagan. The character was previously played by Andrew Terraciano throughout Blue Bloods’ remarkable 292 episode run, making the recast impossible to miss.
Naturally, viewers began asking questions. Why change such a long-established role now?
Co-showrunner Brandon Margolis addressed the decision in an interview with Variety, emphasizing that the choice was never about diminishing Terraciano’s contribution. Instead, it was about reflecting a turning point in the characters’ lives.
“We love Andrew and the work he did over the years on Blue Bloods,” Margolis explained. “This really comes down to telling a new chapter. It’s not just Sean stepping into the family business Danny is now the father of a cop, and that’s a dynamic we’ve never explored before.”
According to Margolis, the creative team saw the spin-off as an opportunity to reframe Sean’s journey and introduce a fresh emotional lens.
“There were all these new storytelling lanes opening up,” he said. “It felt like the right moment to bring in a new performance with a different energy one that helps dramatize how much has changed. It’s still the same character and the same relationship, but the tone is very different now.”
Margolis also praised Amonsen’s interpretation of Sean, highlighting what he brings to the role.
“We love what Mika has brought to Sean that blend of vulnerability and determination, and a real need to prove himself,” he added. “Watching that come to life has been incredibly rewarding.”
With a new face and a deeper father son dynamic at its core, Boston Blue is quickly establishing its own identity while still honoring the family legacy that made Blue Bloods a television staple for more than a decade.