The Sentry Story: Why Steven Yeun Left Marvel's Thunderbolts* And The Shocking Replacement

The news that Steven Yeun was cast as the god-like hero Sentry in Marvel Studios’ upcoming film Thunderbolts* was met with overwhelming excitement, promising a unique and powerful addition to the Marvel Cinematic Universe. However, in a disappointing turn of events that underscores the chaotic nature of Hollywood production schedules, the acclaimed actor ultimately had to step away from the role, leaving fans to wonder what could have been. This article, updated in December 2025, dives deep into the casting saga, the true reasons behind Yeun's departure, and the actor who has since taken on the monumental task of portraying the MCU's most conflicted powerhouse.

The highly anticipated Thunderbolts* film, set to conclude the MCU's Phase Five, was poised to introduce a character often described as "Marvel's Superman"—the Sentry, also known by his civilian identity, Robert "Bob" Reynolds. Yeun's involvement, confirmed by his Invincible and The Walking Dead creator Robert Kirkman, signaled a major shift in the character's on-screen portrayal. The subsequent recasting became one of the most talked-about Marvel stories of the year, cementing the Sentry as one of the most pivotal new characters in the franchise.

Steven Yeun: Biography and Profile of the Departed Sentry

Steven Yeun, born Yeun Sang-yeop, is a Korean-American actor celebrated for his versatile and emotionally resonant performances across film and television. His career trajectory has seen him evolve from a fan-favorite genre star to an Academy Award-nominated leading man.

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• Full Name: Yeun Sang-yeop (Steven Yeun)
• Date of Birth: December 21, 1983
• Place of Birth: Seoul, South Korea
• Nationality: Korean-American
• Breakthrough Role: Glenn Rhee in the post-apocalyptic horror series The Walking Dead (2010–2016).
• Critical Acclaim: Received an Academy Award nomination for Best Actor for his performance in the film Minari (2020).
• Recent Success: Won an Emmy Award for his role as Danny Cho in the Netflix series Beef (2023), which was directed and executive produced by Jake Schreier, who is also directing Thunderbolts*.

Yeun's filmography demonstrates a commitment to complex, challenging roles, making his initial casting as the deeply troubled Sentry a perfect fit. His reunion with director Jake Schreier from the critically acclaimed series Beef added another layer of excitement for the Marvel project.

The Real Reason Steven Yeun Exited the Thunderbolts* Project

The anticipation for Steven Yeun’s MCU debut was palpable, with fans eager to see his take on the powerful but mentally fragile character. However, in January 2024, the news broke that Yeun would no longer be part of the Thunderbolts* cast.

The reason for the departure was clear and a common casualty of the Hollywood production landscape: scheduling conflicts.

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The 2023 SAG-AFTRA strikes caused massive delays across the entire film industry, forcing Marvel Studios to push back the production and release schedule for Thunderbolts*. Yeun, a highly sought-after actor, had commitments to other projects that could not be moved, creating an unavoidable clash with the film's new shooting dates.

Yeun himself explained that the forced time off during the strikes led to "time passing and things shifting," which ultimately made it impossible to commit to the new timeline. While his departure was amicable, it represented a significant loss for the film and the MCU's diversity push.

Who is The Sentry? Unpacking the Marvel Comics Powerhouse

The Sentry, whose alter ego is Robert "Bob" Reynolds, is one of the most powerful and tragic figures in Marvel Comics history. His introduction to the MCU is a game-changer, as his power level rivals—and potentially exceeds—that of characters like Thor and the Hulk.

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The Golden Guardian and His Dark Secret

The Sentry gained his immense powers after drinking a super-soldier serum, a thousand times more potent than the one given to Captain America. This serum granted him the "power of a million exploding suns." His abilities include:

• Incalculable Super Strength: He possesses the strength to subdue the Hulk at his most powerful.
• Flight and Super Speed: Capable of interstellar travel and moving at incredible velocities.
• Molecular Manipulation: The ability to control light and matter at the sub-atomic level.
• Immortality and Regeneration: He can return from death and instantly heal from virtually any injury.

However, this immense power comes at a terrible cost. The Sentry’s power is intrinsically linked to his dark opposite: The Void.

The Void is the Sentry’s malevolent, destructive alter-ego—a cosmic entity of pure darkness that represents Robert Reynolds’ deepest fears and insecurities. The Sentry’s entire existence is a constant, desperate battle to keep the Void contained, often leading him to erase his own memory and the world’s memory of him to prevent catastrophic destruction. This deep-seated mental conflict and duality are what make the character so compelling and why his role in a team of anti-heroes like the Thunderbolts* is so crucial.

Lewis Pullman: The New Actor Stepping into the Void

Following Steven Yeun's departure, Marvel Studios quickly moved to fill the role, ultimately casting actor Lewis Pullman as the new Sentry. Pullman, known for his roles in Top Gun: Maverick and *Outer Range*, faces the daunting task of bringing this complex character to life.

Pullman has expressed the immense pressure and "intimidating" challenge of taking on a character of the Sentry's magnitude and psychological depth. Early descriptions of his costume suggest a faithful, classic comic book look, indicating Marvel is serious about establishing the Sentry as a major player in the MCU.

The Thunderbolts* Team and Sentry's Role

The Sentry is expected to be a major antagonistic force in the film, which features a roster of morally ambiguous characters assembled by Contessa Valentina Allegra de Fontaine. The core Thunderbolts* team includes familiar faces from the MCU:

• Yelena Belova/White Widow (Florence Pugh)
• Bucky Barnes/Winter Soldier (Sebastian Stan)
• Alexei Shostakov/Red Guardian (David Harbour)
• John Walker/US Agent (Wyatt Russell)
• Taskmaster (Olga Kurylenko)
• Ghost (Hannah John-Kamen)

With the film set to premiere in 2025, the Sentry's presence—whether played by Steven Yeun or Lewis Pullman—is designed to provide a high-stakes threat. The team of anti-heroes will likely be forced to confront the destructive power of The Void, marking a critical turning point for the MCU's Phase Five narrative. The initial excitement over Yeun’s casting may have faded, but the character of Robert Reynolds remains one of the most fascinating and powerful additions to the Marvel Cinematic Universe.