Executives fear his reputation could take another pounding at a planned US hearing in January during which he will again face ex-wife Amber Heard over abuse claims she made in the Washington Post.
Now Robert Downey Jr wants Depp – who admitted two years ago that his near £500 million movie fortune was “almost all gone” – to appear alongside him in the third film in the franchise.
A senior source at Warner Bros, which has already set a UK release date of December 24 next year for Sherlock 3, confirmed: “Bob wants Johnny on board, come hell or high water.”
Co-stars Jude Law and Rachel McAdams have signed on to reprise their roles as Dr Watson and Irene Adler, but screenwriter Chris Brancato is yet to finish the script.
Our source added: “Bob’s wife, Susan Downey, is a co-producer and like her husband, she has been a close friend of Johnny, his previous partner Vanessa and their two children for years. She shares Bob’s view that not only is Johnny a stellar talent but he also deserves a helping hand.”
Depp’s troubles have struck a chord with Downey Jr, who hit rock bottom in the late 1990s and early 2000s when he was jailed following a string of arrests for heroin and cocaine possession.
He was also found with an unloaded .357 Magnum handgun after being stopped for speeding down LA’s Sunset Strip. But, following rehab stints, he rebounded with the Iron Man franchise and is now worth in excess of £300 million.
At a recent red carpet premiere, he said of Depp: “There’s nobody I admire more.” Depp said of Downey Jr: “We’ve known each other a million years.We came up through the ranks together.”