When CBS announced Boston Blue, the long-awaited spinoff to Blue Bloods, excitement surged—yet it didn’t take long for one casting decision to ignite debate among fans. Mika Amonsen, the actor stepping into the role of Sean Reagan, quickly found himself at the center of an unexpected storm. Sean, the youngest son of Donnie Wahlberg’s Danny Reagan, had been portrayed by Andrew Terraciano across all 14 seasons of Blue Bloods, making him one of the longest-running characters in the franchise. Recasting such a familiar face was always going to trigger reactions—but few anticipated the intensity.
Amonsen, however, is taking it all in stride.
“There’s been some negativity, for sure,” he acknowledged in an exclusive interview with Us Weekly, reflecting on the early backlash from fans who were surprised—and in some cases disappointed—to see a different actor playing Sean. “But underneath those comments, there are also so many people rallying for Sean, supporting what I’m doing, and saying they’ve really enjoyed this version of the character.”
For Amonsen, stepping into the Reagan family wasn’t just another acting job. It was an inheritance. Blue Bloods, which ran from 2010 to 2024, became one of CBS’s most enduring dramas, in large part because of the Reagan family dynamic. Danny, his late wife Linda, and their sons Jack and Sean were foundational pieces of that universe. Terraciano grew up on screen during the show’s 14-year run, making his take on Sean deeply familiar to audiences who watched him mature from a child actor into an adult.
So when Boston Blue brought Sean back—now older, joining his father in Boston, and entering a new chapter—Amonsen felt the weight of expectation immediately.
“I definitely felt a ton of pressure at first,” he admitted. “I wanted to respect Andrew the best I could. There were even certain visual choices—hair, mannerisms, subtle ways of carrying myself—that I tried to keep because fans associate those things with Sean.”
In the days following his casting, Amonsen did what any actor stepping into a legacy role would do: he started binge-watching Blue Bloods. Instead of starting from the beginning, he focused on the later seasons where Sean was older. “I wanted to get a sense of who he became in adulthood,” Amonsen explained. “Not just his dynamic with Danny, but who Sean was as a person—his energy, his optimism, his resilience.”
The research helped him find unexpected reassurance. “When I watched Andrew’s performance, I noticed we actually share a lot of natural similarities,” he said. “Our energy is upbeat, grounded, and curious. That made me feel like I didn’t have to reinvent myself to play Sean—I just needed to build on what was already there.”
Still, Amonsen knew he couldn’t simply imitate Terraciano. Boston Blue isn’t Blue Bloods. Sean isn’t a teenager anymore. And the Reagans aren’t in New York. This shift gave the actor space to balance familiarity with reinvention.
“I really want to maintain Sean in a way that honors what Andrew created,” he said. “But at the same time, this is a new chapter. We’re exploring a version of Sean stepping into adulthood—new responsibilities, new challenges, a new environment. It’s something the original show never fully explored.”
Showrunners Brandon Sonnier and Brandon Margolis encouraged that approach from day one. According to Amonsen, they emphasized that the heart of the recast wasn’t about replacing Terraciano, but about continuing Sean’s story in a way that fit the new series. “Brandon and Brandon were great about giving me freedom,” he said. “They wanted me to respect the character’s history, but also make him feel alive in the world of Boston Blue.”
Part of that evolution involves Sean’s relationship with his father. In Blue Bloods, Danny and Sean shared a warm but sometimes distant bond, shaped by Danny’s job and the family’s grief after Linda’s death. In Boston Blue, Sean’s journey is more independent—and more intertwined with Danny’s than ever before.
“We haven’t seen this version of their relationship before,” Amonsen said. “Sean’s older now, stepping into new roles, trying to understand who he wants to be. And Danny is navigating his own transition from New York to Boston. They’re both in unfamiliar territory, which makes their dynamic deeper and more complex.”
While fan reaction at first was mixed, the conversation has evolved. Many viewers have welcomed the fresh energy Amonsen brings, noting that he captures Sean’s core traits while adding maturity that reflects the character’s growth. And as the show continues to build its identity, audiences have begun to embrace this new chapter rather than compare it to the past.
For Amonsen, that acceptance means everything. “Fans loving where the show is going, especially when it comes to Sean, makes me really happy,” he said. “I know how important this character is to people. I don’t take that lightly.”
With Boston Blue establishing itself as the next major chapter in the Reagan family saga, the decision to recast Sean—once controversial—now feels like an essential part of the franchise’s evolution. And while Andrew Terraciano’s portrayal will always be cherished, Mika Amonsen is forging his own path with respect, thoughtfulness, and a clear understanding of the legacy he has stepped into.
“Ultimately,” he said, “I’m just trying to honor what came before while exploring who Sean can become.”
Boston Blue airs Fridays at 10 p.m. ET on CBS.
