Donnie Yen's role in John Wick: Chapter 4 is more significant than it appears. John Wick (Keanu Reeves) is headed into battle against the High Table in John Wick: Chapter 4, with more henchmen than ever being unleashed to oppose him. John will also have allies on his side, including his ally in the Continental Winston (Ian McShane), while his old friend Caine (Donnie Yen) is more ambiguous in his relationship with John.

John Wick: Chapter 4's trailer includes character moments like Caine conversing with John in a church, telling him "You're going to die John," with the two later seen in a gun and sword fight. However, Caine specifically being described as an old friend of John's adds another layer of complexity to his role in John Wick: Chapter 4. This all suggests that Caine's character will be a very pivotal one to the story of John Wick: Chapter 4.

RELATED: Donnie Yen's John Wick 4 Fighting Style Could Be A Franchise First

Donnie Yen's Character Could Have A Unique StoryDonnie Yen John Wick 4

As an old friend of John's, Caine's terse conversations with John and fight scene with him in the trailer suggest they have had some kind of falling out in the past. This is not necessarily a major revelation, as John Wick's biggest personal issue is his apparent habit of having friendships end on bad terms. The question is whether Caine will remain John's enemy by the end of the movie.

John was able to call upon the help of his embittered friend Sofia (Halle Berry) in John Wick: Chapter 3 - Parabellum, albeit only with a marker that required her to honor a past favor he paid to her. Still, John might make similar efforts to mend fences with Caine in John Wick: Chapter 4, with their church conversation indicating the possibility of peace between them. If John is able to bring Caine back to his side in John Wick: Chapter 4, Caine's story could potentially make him a friend-turned-enemy-turned-friend-again of John Wick's.

John Wick 4 Might Show More Of John's Past

Keanu Reeves in the John Wick: Chapter 4 trailer

The history between John and Caine could also shed more light on the former's past. Throughout the John Wick franchise, John is referenced as the legendary Baba Yaga by his fellow assassins, with stories of John slaying enemies with such mundane items as a pencil illuminating his reputation. Despite this, precious little of John's life prior to his retirement as an assassin has actually been revealed in the John Wick movies (though the John Wick comic book mini-series has explored stories of his past), and Caine could change that.

Depending on how long they have known each other, John and Caine's relationship could reveal more than ever about John Wick. Whether John and Caine once worked as partners or trained together in their early assassin days, Caine could be the key to bringing the full scope of John's backstory to the big screen in John Wick: Chapter 4. Even better, with such significance to the story, Caine might even point to John Wick's ending not being so bleak.

More: John Wick 4 Is Finally Unleashing The Franchise's Massive Universe

Key Release Dates