Spider-Man: Brand New Day will usher in a new X-Men era by introducing one key mutant in Tom Holland's upcoming MCU movie. While Spider-Man 4 kicks off a fresh new chapter for Peter Parker, a major point of discussion among fans is the mystery surrounding Sadie Sink's still-unnamed MCU character. There are already many theories on who Sink is playing in Brand New Day, with some speculating that she could be either Gwen Stacy, a shapeshifting villain named Shathra, or even Mayday Parker. What makes Sink's character more intriguing is the report claiming she is part of Avengers: Secret Wars, further proving that she is a key piece in the MCU's future.
Entertainment insider Cryptic HD Quality shared on X that Sadie Sink portrays the MCU's Jean Grey in Spider-Man: Brand New Day, meaning that her inclusion signals the true beginning of a new era for the X-Men in the Marvel Cinematic Universe.
Jean Grey's inclusion in Spider-Man: Brand New Day is quite significant. Not only does it represent a new era, but her casting also seems to confirm that the MCU will lean toward a younger generation of X-Men in the post-Secret Wars timeline.
Interestingly, in October 2025, the first glimpse of Sadie Sink's mystery MCU character was spotted on set. The actress was seen sporting red hair and wearing camouflage pants and boots, sparking theories that she was Jean Grey.
The fact that Jean Grey is thrust into the street-level world of Spider-Man indicates that mutants in the MCU are slowly emerging and already present, but they chose to hide due to the existence of organizations like the Department of Damage Control (a key mutant-hunting villain). This is important because other major characters, like the MCU versions of Cyclops and Professor X, could already be present in Earth-616.
Directed by Destin Daniel Cretton, Spider-Man: Brand New Day continues the story of Peter Parker as he fights a plethora of villains while still trying to find the right balance between his normal and heroic life. The movie premieres in theaters on July 31, 2026.
Why It's Significant that Spider-Man 4 Begins X-Men's New Era
Tom Holland's Spider-Man is perhaps the most recognizable MCU hero today, and it is all but a guarantee that many fans will flock to theaters to witness his next adventure in Spider-Man: Brand New Day.
Introducing Sadie Sink as Jean Grey in the film is a bold yet understandable risk, and it makes sense for both Marvel Studios and Sony Pictures to do so, as it would add generational hype to the MCU's next chapter: the Mutant Saga.
Jean's upcoming debut in a Spider-Man-focused story positions her as a necessary bridge between the street-level heroes (due to her rumored close ties with the Punisher) and the larger mutant community, which could pave the way for more crossovers in the future since Marvel appears to be leaning toward prioritizing both narratives in the post-Secret Wars timeline.
Jean's imminent appearance in Brand New Day also changes everything because it would allow Spider-Man to learn more about the mutants, making the web-slinger an ideal candidate to crossover into future X-Men stories.
All in all, Spider-Man: Brand New Day being positioned as the launchpad for X-Men's new era sounds fitting, and it seems to be a deliberate narrative decision, given Marvel Studios' transition to a more active integration of mutants. By doing this, fans will be more familiar with them even before the eventual release of the MCU's upcoming mutant-focused movies.
