The "Nightcrawler" star was being courted to replace Tom Hardy, who last week dropped out of the DC Comics-inspired movie. Gyllenhaal was said to be director David Ayer's favorite to play the Suicide Squad's leader in what's been described as the "'Dirty Dozen' with supervillains.
It was initially speculated Hardy's departure might've been tied to his involvement in Alejandro Gonzalez Inarritu's frontier drama "The Revenant," whose shoot appears to be running longer than planned. However, a rumor emerged over the weekend that the actor was unhappy with the finished script, which, with the addition of Will Smith and Jared Leto to the cast, expanded the roles of Deadshot and The Joker, effectively making Rick Flag a supporting player.
"Suicide Squad" is set to begin shooting in April in Toronto, with the confirmed cast rounded out by Margot Robbie as Harley Quinn, Jai Courtney as Boomerang and Cara Delevigne as Enchantress. Viola Davis is reportedly nearing a multi-picture deal to play Amanda Waller.
Gyllenhaal, who's collected a string of awards nominations for his performance in the crime thriller "Nightcrawler," has at least three films scheduled for release this year: "Southpaw," "Everest" and "Demolition."
"Suicide Squad" opens Aug. 5, 2016.