100 Episodes Later, NBC Has Yet To Get Over One Chicago's Biggest Loss

Published Oct 24, 2026, 11:16 AM EDT Laura Hurley has been writing about the entertainment industry for more than twelve years, after a decade as a content producer and editor at CinemaBlend after writing for WhatCulture and Examiner. Attending events like SCAD TVfest and San Diego Comic-Con over the course of her career, she has been immersed in the world of network, streaming, and cable TV. NBC's One Chicago universe has run for nearly 800 episodes across four shows since 2012, but one particular Chicago Fire departure stands out as the franchise's biggest loss. Chicago Fire was the show that started it all, when Dick Wolf's TV franchise expanded beyond the Law & Order series in New York City to follow the action in the Windy City. Even after Chicago P.D. and Chicago Med followed, Fire held on to most of its original cast for 200 episodes. Now, with another major milestone approaching, the franchise's big loss feels as fresh as ever. All three current One Chicago shows returned for new seasons in NBC's fall 2026 premiere schedule, and the weeks are counting down until Chicago Fire airs its 300th episode. Within the Wolf Entertainment world, only Law & Order and Law & Order: SVU have run for longer. Season 15 was the start of a new era for this firefighting procedural drama, thanks to the arrival of a new showrunner and the looming exit of a longtime Chicago Fire star. Still, even as the future looks bright for the series, its previous loss of another core member of Firehouse 51 still stings. Jesse Spencer was Chicago Fire's top-billed star for the first ten seasons, and Matt Casey's central role at Firehouse 51 reflected it. He built some of the strongest relationships within One Chicago, both romantically and platonically. Even though Fire was able to explore new storylines like Kidd becoming the lieutenant of Casey's old rig in the wake of his exit, the drama hasn't managed to fully fill the void he left behind back in season 10. Casey Left During Chicago Fire's 200th Episode MoveStillsDB Chicago Fire treated Jesse Spencer's exit like the TV event that it was, by putting his character's final day at Firehouse 51 at the center of the milestone 200th episode in 2021. Casey had already made the fateful decision to leave Chicago in order to care for the children of a fallen firefighter, and Spencer only returned as a regular for the first five episodes of season 10. That was still enough for him to reach episode 200, and get the kind of fanfare Casey deserved. Importantly, he also left the door wide open to return to the CFD within just a few years, so his exit was much more bittersweet than how Fire wrote out characters like Lauren German's Shay and Yuri Sardarov's Otis. He got to say goodbye to Boden and Severide, and Casey's departure didn't result in the end of his romance with Brett. In fact, the ending was open enough in the 200th episode that Spencer returned as a guest in another four episodes. For better or worse, Casey is gone but not forgotten, nearly 100 episodes after he left the CFD. Why Casey Is Firehouse 51's Biggest Loss Courtesy of MovieStillsDB Jesse Spencer was the top-billed Chicago Fire star for a reason, and it wasn't entirely clear just how essential he was to the drama until he was gone. Despite veering off the beaten path more than a few times over his ten seasons, Casey was the most reliable leader among Chicago Fire's ensemble of characters, other than Chief Boden himself, and fans got to follow along as he went from lieutenant to captain. He was steadfast and thoroughly dependable as the officer on Truck 81. That said, the biggest void he left behind involved his relationships. Casey's romance with Dawson was arguably the most central love story of the entire franchise over the six seasons before Monica Raymund's exit, and Spencer deserves credit for building a believable new romance with Kara Killmer's Brett in the subsequent years. The biggest relationship to disappear in the aftermath of his departure wasn't one of his romances, however. It was the loss of the friendship between Casey and Severide. Not only was it touching to see their relationship grow from adversarial to brotherly in the earliest seasons of Chicago Fire, but Casey as the most reliable officer at Firehouse 51 allowed Severide to be more of a maverick as his Squad 3 counterpart. Both characters got more fun and funnier when they were together, and it's still easier to picture Casey as the leader of 51 than Severide. Plus, even though Chicago Fire built the "Stellaride" relationship into one of the strongest in One Chicago, Severide's biggest storylines have been almost exclusively with Kidd over the past several years. There was a lot more to Severide than Kidd, OFI, and leadership burdens when he had Casey by his side, and both characters were richer for that relationship. Chicago Fire has had five seasons and 100 episodes to fill the void left by Casey as the franchise's biggest loss, and it hasn't happened just yet. For now, fans can look forward to the build up to episode 300 on NBC's One Chicago Wednesdays at 9 p.m. ET. Release Date October 10, 2012 Network NBC Showrunner Andrea Newman Cast Taylor Kinney Kelly Severide David Eigenberg Christopher Herrmann Directors Michael Brandt Writers Michael Brandt Creator(s) Michael Brandt, Derek Haas