On April 22, Vin Diesel posted a 19-second video to Instagram recapping the first week of production on “Fast X,” the latest entry in Universal’s 21-year-old franchise. In the clip, Diesel sidles up to Justin Lin to ask the film’s director and co-writer how he’s feeling at the end of the first week of production.

As Diesel grins into his selfie camera, Lin, seated and seemingly uncomfortable, nods his head as he tries to find the right words.

“It feels like the beginning of, uh, of an epic ending,” Lin says flatly.

On the surface, Lin was referencing the planned back-to-back filming of the action franchise’s 10th and 11th installments, which are purportedly meant to conclude the saga of Diesel’s Dominic Toretto and his “Fast” family.

Instead, Lin, who has helmed five of the franchise’s ten installments, was perhaps accidentally foretelling the end of his time at the wheel of “Fast X.” Just four days later, the 50-year-old filmmaker announced that he would no longer direct the movie.

“With the support of Universal, I have made the difficult decision to step back as director of ‘Fast X’, while remaining with the project as a producer,” Lin said in a statement posted to the movie’s official social media handle.

The news came as a massive shock to fans, who have come to see Lin as one of the primary architects of the series’ approach to heart, humor and vehicular carnage since he boarded the project with 2006’s “The Fast and Furious: Tokyo Drift.” He’s since helmed some of the most critically acclaimed installments, including 2011’s “Fast Five,” and took the films’ stunts to new — and quite literally out of this world — heights with his 2021 return “F9: The Fast Saga.”

Lin’s exit was reportedly “amicable” and chalked up to “creative differences.” But leaving a multi-million franchise days into production has put Universal in the rare and unenviable position of finding a replacement in time to make their planned May 19, 2023 theatrical release date.

Representatives for Universal did not immediately respond to requests for comment.

The biggest challenge facing the production is time. Sources tell Variety that the second unit will continue production in the U.K., while the main unit is paused until a replacement director is hired. Until then, the production is burning through cash to keep key crew and cast members in limbo. Sources from different studios with experience replacing directors midstream estimated that it could be costing Universal upwards of $600,000 to $1 million a day. Much of the cost depends on whether production on any major set-pieces were already underway — the bigger the action beats, the more pricey the delay — which suggests that Lin made his decision to vacate the director’s chair so early into the shoot to avoid even bigger cost overruns further down the production calendar.

There’s also the matter of the franchise’s newest stars, Jason Momoa and Brie Larson, as well as Charlize Theron, who’s returning for a third appearance as the villain Cipher. All three are dedicated to ongoing franchises that require their time and attention, so delays could necessitate some hasty, and costly, changes to accommodate their busy schedules.

Observers have noted that Lin’s announcement was made on the “Fast and Furious” social media channels, rather than by Lin’s reps or on his personal social media — and it was formatted in the franchise’s official font. Given the formality involved, it’s likely that Universal had some advance notice of his decision, and therefore more time to begin seeking a replacement.

The most logical answer to replace him would be to slot someone in who’s already familiar with the franchise’s mechanics. The problem is that, other than Lin, only five directors have helmed a “Fast and Furious” movie: Rob Cohen (2001’s “The Fast and the Furious”), the late John Singleton (2003’s “2 Fast 2 Furious”), James Wan (2015’s “Furious 7”), F. Gary Gray (2017’s “The Fate of the Furious”) and David Leitch (2019’s “Fast & Furious Presents: Hobbs and Shaw”).

Wan, Gray and Leitch would all be viable options — if they weren’t busy. About an hour after the news broke that Lin was stepping down as director, Wan was onstage at CinemaCon Las Vegas sharing a sneak preview of Warner Bros.’ “Aquaman and the Lost Kingdom,” which is still in post-production and set for a March 2023 release. That film has elaborate special effects, making it nearly impossible that Wan could turn his attention elsewhere. Gray is currently filming Netflix’s “Lyft,” starring Kevin Hart, and Leitch is set to start production on Universal’s “Fall Guy” with Ryan Gosling imminently.

Meanwhile, Cohen hasn’t directed a film since 2018, shortly before becoming embroiled in personal controversy with multiple allegations of sexual assault. (Representatives for Cohen have denied these claims).

A rival studio executive speculated that Universal could look for a skilled second-unit director, particularly one well-versed in big-budget action movies, to come on board to oversee the sequel. An A-list filmmaker might not be willing to join the series without demanding changes to the script or additional time to find their way into the story.

Beyond that, it’s well known that Diesel, the “Fast and Furious” OG, is the real driver of the franchise. He’s also a producer on the film and has not been shy about publicly expressing his displeasure with creative decisions made by others. On April 20, Diesel posted that the first draft of the “Fast X” screenplay, presumably written by Lin and co-writer Dan Mazeau, did not include Jordana Brewster’s character Mia, who, as fans know, is also Dom’s sister. “I was so disappointed that I couldn’t see how I could continue,” Diesel wrote. The actor got his way and Brewster ended up joining the film.

There were other speed bumps on the way to production for “Fast X,” including Diesel’s feud with Dwayne Johnson, who joined the crew with “Fast Five,” and then famously refused to share the set with him for “Fate.” When Diesel made a public overture to Johnson about returning for the new film, Johnson — just as publicly — shut it down.

“I told [Diesel] directly that I would not be returning to the franchise,” Johnson said in a CNN interview. “I was firm yet cordial with my words and said that I would always be supportive of the cast and always root for the franchise to be successful, but that there was no chance I would return.”

Diesel also attempted to recruit Rita Moreno to the movie’s cast as Dom’s abuela, but scheduling kept the EGOT-winner from making an appearance. “I said, ‘I’ll take a rain check,’ and we’ve become friends,” Moreno told Variety in March.

Despite his influence, however, the chances that Diesel would end up getting the director gig do not seem high. Although he did helm the 2009 short film “Los Bandoleros” — a prequel to Dom’s return to the franchise in 2009’s “Fast and Furious” after sitting out the second and third installments — Diesel has only directed a single feature, 1997’s “Strays.” Universal will almost surely need a more experienced hand to take over such a giant production that is already underway.

Certainly, the actor’s ambitions for “Fast X” are clear. In his video with Lin, he asks the filmmaker, “Is it fair to say that this will be the best one?”

Lin shrugs. “In my heart, yes.”