Now that Ben Affleck won't direct himself as Batman, who will?

There's a reason that actors don't direct themselves as the title star of a superhero film. And now, Ben Affleck has decided that he shouldn't pull such double duty.

Affleck has just stepped out of the director's chair for the next solo Batman film, as Variety was first to report.

Affleck will still star as Batman in future WB/DC Entertainment films, including the next solo Batman film, which still has no release date. And the Oscar-winning filmmaker will next appear as the Dark Knight in Justice League this November.

Affleck's first appearance as the Caped Crusader, in Batman v Superman: Dawn of Justice, was considered a highlight of the film by many fans, as the actor defied sceptics who had pointed to his lesser work in Daredevil many years earlier.

Affleck also appeared as Batman in last summer's Suicide Squad, establishing the character's connection with the new Joker (Jared Leto) and Harley Quinn (Margot Robbie).

Suicide Squad director David Ayer is set to direct Robbie in Gotham City Sirens, a movie rumoured to feature classic Batman villains Poison Ivy and Catwoman alongside Robbie's Harley Quinn. Sirens could potentially include another Affleck/Batman appearance, given the character's history with those bat-villains.

But who will direct a solo Batman film?

Now responsible for taking the popularity of Robbie's Harley Quinn and turning it into a potential multi-movie franchise, Ayer more than likely won't be a candidate to direct Batman's solo go.

Man of Steel, Batman v Superman and Justice League director Zack Snyder also isn't a probable candidate. Snyder's DC films (including Watchmen) have been visual spectacles, but they have been criticized for their handling of story, and his Batman v Superman performed below studio hopes at the box office.

Director Zack Snyder on the set of Watchmen. Photo / Clay Enos

Justice League could be Snyder's last WB/DC offering, depending on how the film is received.

In the right hands, a Batman movie franchise can be a billion-dollar property for WB/DC, as Christopher Nolan's "Dark Knight" trilogy proved.

And elements are in place for the next solo Batman film to be a hit. Affleck has established himself in the role; his Batman is the closest thing to the Batman of the comic books jumping out of the page - more than any other cinematic caped crusader.

A villain for the next Batman film is in place, with Joe Manganiello set to play DC Comics assassin Deathstroke, while Jared Leto's Joker also might appear.

And Batman v Superman and Suicide Squad confirmed the Joker and Harley Quinn's involvement in the murder of Batman sidekick Robin. The death of Robin (Jason Todd) and Robin's return from the grave as the Red Hood, seeking lethal revenge against the Joker, could be an option for a solo bat-film plot.

One of DC Comics' top writers, Geoff Johns, is now president of DC Entertainment, and he will have a greater role in all WB/DC movies going forward, greatly increasing the likelihood that the essence of what fans enjoy most from Batman in the comics makes it to the big screen.

Meanwhile, Affleck's latest actor-director turn, Live by Night, just bombed badly - a disappointment that had to have factored into his decision not to direct himself as Batman. This is his first true stumble, after all, as a director, after the well-received Gone Baby Gone, The TownArgo.

But playing one of the biggest superheroes - with an entire studio depending on you to get it right for the sake of its connected superhero movie universe - is enough stress.

And by taking himself out of the director's chair, Affleck can focus entirely on delivering as a performer.

Jettisoning such double duty could well prove to be his smartest feat as Batman.