Actor Vin Diesel, who plays Groot in the Marvel Cinematic Universe, has penned a tribute to Avengers: Endgame co-star Robert Downey Jr.

After praising Downey Jr.'s attitude and spirit on Instagram, Diesel gave a specific example of something the Iron Man actor said to him: "On the weekend of the highest grossing movie of all times he in the most humble way says, your next brother. Fast 9 is going to take the industry to new heights! His belief in me sometimes scares me." Diesel then expressed his gratitude and his "brotherhood." The photo Diesel shared shows him and Downey Jr. taking a selfie.

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Diesel's post makes several references to his upcoming Fast & Furious films, which have overall performed exceptionally well at the box office. Fast & Furious 9 will be helmed by Justin Lin, who directed the third, fourth, fifth and sixth entries in the Fast & Furious franchise. Fast & Furious 9 is slated for a 2020 release.

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Directed by Joe and Anthony Russo, Avengers: Endgame stars Robert Downey Jr. as Iron Man, Chris Evans as Captain America, Mark Ruffalo as Bruce Banner, Chris Hemsworth as Thor, Scarlett Johansson as Black Widow, Jeremy Renner as Hawkeye, Brie Larson as Captain Marvel, Paul Rudd as Ant-Man, Don Cheadle as War Machine, Karen Gillan as Nebula, Danai Gurira as Okoye and Bradley Cooper as Rocket, with Gwyneth Paltrow Pepper Potts, Jon Favreau as Happy Hogan, Benedict Wong as Wong, Tessa Thompson as Valkyrie and Josh Brolin as Thanos. The film is in theaters now.