Fans of Blue Bloods have been able to see some of their favorite characters return during the 2025 TV schedule, thanks to spinoff series Boston Blue. In addition to Donnie Wahlberg, who stars as Detective Danny Reagan, Bridget Moynahan reprised her role as Erin Reagan in the premiere, while Marisa Ramirez has been recurring as Maria Baez. The show also brought back Danny’s youngest son, Sean, though he’s now played by Mika Amonsen, who’s opening up about taking over the role.
When it was announced that Amonsen would be playing Sean in Boston Blue, it came as a surprise. Andrew Terraciano played the character during all 14 seasons of Blue Bloods, while his big brother, Tony, played Sean’s older brother, Jack. Boston showrunners Brandon Margolis and Brandon Sonnier previously explained the recasting, saying that it had to do with picking up the series with the story in progress and showing that Sean went through the Academy, which made sense. But it was a stressful time for Amonsen when he landed the role, as he recalled to Us Weekly:
I definitely felt a ton of pressure at first. I felt the pressure to respect an actor before me because I wanted to respect Andrew the best I could. There were even certain visual choices that I made that I wanted to keep in terms of hair styling and certain ways of being [as Sean]. I really want to maintain Sean as close as I can in the ways that I do it out of respect for this character that everyone loves — but also the character Andrew built.
Considering Terraciano portrayed Sean for 14 years, I can imagine how it wouldn’t be easy for someone else to just come in and play the character Amonsen not only tried to keep the mannerisms consistent but the styling choices as well. Overall, it seems like he also took great care in making sure that his portrayal was as close to Terraciano’s as he could with the little time he had to prepare:
When I booked the show, it all happened really quickly. It was within about a week’s time, and I was really thrown into it quickly. I did binge-watch as much as I could, and I found doing the later seasons was more helpful. I wanted to get a sense of who Sean was toward the end of the show. I really wanted to get a sense of his character at that point into adulthood and his relationship with Danny.
Despite not having a lot of time to really study the character, Mika Amonsen has been able to not only hone in on what makes Sean and Danny’s relationship work. In the process, Amonsen has also been able to show people who Sean Reagan is all while putting his own spin on the character.
Of course, Andrew Terraciano laid the foundation, and Amonsen shared he wanted to pay as much respect to him as he can while also doing his own thing. And the longer he studied, the more he realized there was actually a lot he and his predecessor had in common:
I wanted to respect Andrew’s portrayal of Sean as much as I could — but also adding something to my own version. The showrunners, Brandon Sonnier and Brandon Margolis, have been really good at giving me a lot of freedom to explore that new dynamic with Donnie. Watching Andrew’s performance, I actually noticed a lot of similarities just between us as people, and our energy. It’s quite upbeat. I have a lot more of an upbeat energy myself. So that was a bit comforting. I definitely kept that within myself and didn’t feel like I was obligated to change that part of me — which was nice — in terms of making it my own.
Not only was Amonsen joining a series that was expanding upon a drama that ran for 14 years, but he was also taking over a character that fans have known for just as long. Additionally, this series is putting a lot more focus on Sean than Blue Bloods, as he’s now a rookie with the Boston PD. Just recently he even received his own love interest, which should spice up his life a bit.
For some fans, it may take time to get accustomed to Sean being played by another actor. However, only a handful of episodes into Boston Blue‘s run, Amonsen is proving he’s the right person to carry the torch. It should be entertaining to see what else he brings to the table as the series continues.
New episodes of Boston Blue air on Fridays at 10 p.m. ET on CBS, and episodes are later made available to stream with a Paramount+ subscription.