Speaking on Jimmy Kimmel’s chatshow last night, Affleck spoke out for the first time since he tweeted his best wishes to Reeves at the time of the initial announcement.
He explained: "I tried to direct a version of it and worked with a really good screenwriter, but just couldn't come up with a version. I couldn't crack it.
“And so I thought it was time to let someone take a shot at it.
Asked later if there was anything he wanted to add, Affleck said only: “I am not Batman.”
Reeves, meanwhile, has recently spoken about what he has planned for the blockbuster.
"It's very much a point of view-driven, noir Batman tale," he teased.
"It's told very squarely on his shoulders, and I hope it's going to be a story that will be thrilling but also emotional. It's more Batman in his detective mode than we've seen in the films.
"The comics have a history of that. He's supposed to be the world's greatest detective, and that's not necessarily been a part of what the movies have been."
While Kit Harington has been picking up a lot of support in recent days, Jake Gyllenhaal remains the frontrunner with many outlets - including Ladbrokes, who list him at 3/1.
Armie Hammer and Michael B Jordan have also been touted as potential replacements for Affleck.