Warning: This article contains spoilers for Wednesday's episode of Chicago Fire, "Double Red."

As the credits rolled on Wednesday's episode of Chicago Fire, Firehouse 51 bid adieu to paramedic Gianna Mackey (Adriyan Rae), who found a new place of employment where there were opportunities for advancement.

"It's always fun to introduce a new character who brings in new dynamics to the show, and we had fun bringing Mackey to life, especially with her connection to Cruz [Joe Minoso]," series creator and executive producer Derek Haas tells EW exclusively.

"Adriyan let us know she had some private reasons to leave Chicago," he continues. "To hear that as a showrunner, you absolutely respect what an actor needs. All I can say is we love her and I know she's going to be great on some other series. And she left 51 on great terms, so there's a chance we could check in on her. We're always looking for something to boost up a crossover! I don't think we've seen the last of Mackey in Firehouse 51."

Chicago Fire
Adriyan Rae and Kara Killmer in 'Chicago Fire'
| Credit: Adrian S. Burrows Sr./NBC

Saying goodbye to Mackey may bring back some unresolved feelings of loss after Gabby Dawson's departure in season 7 — although Monica Raymund, who portrayed Dawson, has popped back in to visit.

This season, Gabby's presence has been felt intensely as her best friend Sylvie Brett (Kara Killmer) and her ex Matt Casey (Jesse Spencer) play the will-they, won't-they game. In last week's episode, Sylvie confronted a jealous Matt, who was treating newcomer Lt. Greg Grainger (Jon Ecker) like trash because he noticed Sylvie and Grainger flirting.

Sylvie told Matt in a very matter-of-fact way that he should sort out his feelings for his ex-wife instead of taking out his frustrations on others. Burn!

"I have nothing but respect, admiration, and love for Monica Raymund, so I've kind of kept that door open at all times," Haas says when asked if she could make an appearance this season. "Anytime she wants to swoop in and steal our hearts again, we'd love to have her."

He adds, "I have some plans this year but they're schedule-dependent, so I don't have a lot to tease in case something doesn't happen. Let's just say I definitely have my eye on the end of the season."

Chicago Fire
Jon Ecker in 'Chicago Fire'
| Credit: Adrian S. Burrows Sr./NBC

Ecker's Grainger has been received with open arms by fans, but is he just serving as a catalyst to bring Sylvie and Matt together? Or might he stick around longer?

"He's been great, and I would not dismiss him out of hand," Haas says. "I could see him having a long life on Chicago Fire, so that's for us to figure out. As the world keeps turning, we're always looking for people like Jon, who has such a rabid fanbase. He's really been awesome. I love watching him work and what he brings. I have a funny feeling if we don't find a place for him on Chicago Fire soon, he's going to be the star of some other show. He has a great vibe and so much charisma."

Meanwhile, Stella Kidd (Miranda Rae Mayo) is back on the up and up with her man Severide (Taylor Kinney), so now she can focus on preparing to take the lieutenant's test.

"She's going to have a gigantic episode coming up, a real emotional one that leads into her taking that test," Haas says. "There's also an opportunity ahead to meet one of her firefighter heroes in real life that's coming up."

Chicago Fire's current season (its ninth) will be shorter than usual, and there are still plenty of stories that need to be explored. Earlier this season, it was revealed that Cruz's wife is pregnant with their first child. Will fans get to meet their baby boy before the finale?

"That's a tough question," Haas says. "We have a big finale coming, that's all I'll say. We're Chicago Fire, and we don't ever give you everything you want. The finale is going to be rough, I'll say that."

Check out our daily must-see picks — plus news, celeb interviews, trivia, and more — in EW's What to Watch podcast, hosted by Gerrad Hall. 

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