"[It feels like] a new show even though it's season five," the actor tells THR about the cast and showrunner changes on the upcoming season.

Jon Seda is back at Chicago P.D. for season five, but a lot has changed at the NBC cop drama since he last reported for duty at the 21st District.

The actor left midway through season four to join the new spinoff Chicago Justice as a series regular. For Seda, it meant getting to help launch the latest part of Dick Wolf's impressive NBC scripted slate, and also only have to split screen time among five series regulars rather than nine.

However, Justice was canceled in late May after just 13 episodes and now Seda returns to a very different P.D. Co-creator and longtime showrunner Matt Olmstead has since exited for a lucrative deal at ABC Studios, replaced by Rick Eid (Law & Order: SVU), and series regular Sophia Bush, who played the beloved Det. Erin Lindsay, has departed after four seasons, subsequently replaced by former Revolution star Tracy Spiridakos following a two-episode arc at the end of last season.

"It feels like I never really left yet it still feels new at the same time," Seda tells The Hollywood Reporter of the season five refresh. "It's like going back to an old team but it's new, so it's exciting."

Ahead of the show's return, Seda spoke with THR about Justice's early demise, why he was almost ready to "move on" from Antonio and a possible rekindled romance with Brett (Kara Killmer).

What was your reaction when you heard Justice wasn't coming back? How surprised were you?

I was hoping for it to come back and get another shot. We only had 13 episodes, so [it's] hard to really get the rhythm going with just 13 episodes in. It was kind of thrown all over the place where episodes we shot early appeared in the middle and some we shot late aired first. Yet it was doing pretty well, I think it was averaging 6 million viewers on Sunday. That said, I think had it been given another shot and another season, it would have done better. You never want to see a show fail and not come back. But I don't think we even look at it as a failure. It just didn't get a second season, but it did well. I got to work with great people, another great group of actors who were just incredible, the crew was amazing so it was a little bittersweet. I'm a team player. I was looking at it like, 'If I can help the One Chicago [universe] going over there, that's great. I'm honored by the fact that Wolf [Films] and NBC looked at my character as a character that could help another spinoff.' So, like I said, it's bittersweet. I'm glad to be back, I'm humbled to be back, very thankful to be back, but I kind of wish I could have brought everyone from Justice back with me.

How soon after Justice was canceled did you hear from producers about coming back to P.D.? How did those talks begin?

I believe it was in the same week. It was pretty quick, which was cool. I was very thankful. If I had to move on, I was going to move on and then I was very thankful for the time that I had. Actors hope to get one year of a show and here I started on Fire and that turned into four years of P.D. and then Justice, so it was a great opportunity, and if that was all it was going to be, I was very happy for that. But for them to come back and really show their support and wanting to have me back, it's just really incredible. I'm really thankful.

How has it been adjusting to the changes among the cast?

The great thing about it is we try and get as close to reality as we can. In reality in these departments, people change. Some move up, some come back, some leave for a certain amount of time, so it's very similar. The heart of it is the unit itself and keeping that unit doing the job the best they can. So like with Sophia, [Erin] was a great character that she created and [she was] a great person to work with, but you don’t look at it like you're trying to fill those shoes. You just change things around and try to keep the unit going.

How does your character come back to the unit?

I think they ran through so many different possibilities and it came down to something kind of simple. It's, like I said earlier, in that line of work, people come and go for whatever reason. There's a case that the Intelligence team is working on in the first episode where it kind of gets stuck with the suspect and how to get close to a certain suspect and they need someone that can really do great undercover [work], and hasn't been seen by this suspect, has no connection and Antonio turns out to be that person. That leads to series of events that will land him back with Intelligence.

What can you say about that dynamic with Voight going forward? How do things change when Antonio comes back?

It's like a yin and yang type of thing. It's been five years now that they've grown with each other, from that place that they came from where Antonio arrested him. They've learned a lot with each other. Sometimes, like in life, you don't choose the family you're born into, but you get to choose the ones you call family, and who would have thought that that would be the case [here]. But yeah, they're like brothers. They're not going to agree all the time, but I think that's something also that's going to be reflected in season five; they’re going to have a little more of that tension that was there between Voight and Antonio, but it's going to be different now because now it's tension after five years of working with each other. It's wanting the best for each other but sometimes, the hardest person to get to understand what's the best way is that person that is so close to you. With all the changes in Chicago right now — which we are going to reflect on the show like with police reform — it's tough to be a cop in the nation, let alone in Chicago. The Intelligence Unit has operated a certain way for a while and now things have to change. How well is Voight going to deal with that? That's another big plus of having Antonio back because he's able to balance. He doesn't want to see the unit fall apart, he wants to help keep it together.

One of the things people really latched onto last season was the Brettonio romance. What do you think brought about that reaction?

Last year when they came to me with the idea of Antonio going to Justice, that was also presented that they had come up with the idea of pairing Antonio and Brett. I remember my initial reaction was, "Wow, I didn’t see that coming." It's not something I would have thought of. And I think that actually turned out to be the beauty of it. I think the fact that they're not your typical type, that you wouldn't think to pair them — that's what made it really interesting. And Kara Killmer, she's just such a great talent and I love working with her. I think she's so great. I had a lot of fun with the Brettonio.

Has there been any talk of rekindling that this season?

There's always that possibility. I'm back, she's there. Antonio's still single and I believe she is. Look, that's not up to me, but if they wanted to entertain that and bring it back, I'd have no problem with them wanting to do that, so we'll see.

You also have a new showrunner this season in Rick Eid. How has it been coming back to the show but with a new voice behind the scenes? Especially after having worked with Matt on both Fire and P.D.?

Yeah, a lot of changes. I wasn't there last year when most of these changes were happening, which lends to it really feeling like a new show even though it's season five. Rick Eid is an incredible talent, he's done so many things and is so experienced with the Wolf shows. He's someone that, in regards to law enforcement, has done so many projects so this fits with him well. He's a real hands-on person, he's there, and just really wanting to make sure that the well-oiled machine that was created, not just keeps running but runs even smoother and finding different ways to get it to go faster and stronger.

We also have Eriq La Salle who has come on now, and he's not just a really good director but he's someone who, from ER, knows this world and he knows both sides of the camera. So he knows how to talk to the actors, and he really cares and nurtures the stories and tries to make sure the heart of the show, which is the stories of these people, aren't getting lost in the action.

Chicago P.D. returns Wednesday, Sept. 27, at 10 p.m. on NBC.