This fall Fox will attempt to (re)capture lightning in a bottle when the network debuts its version of the buddy cop drama Lethal Weapon (Wednesday, Sept. 20 at 8/7c), based on the beloved film franchise starring Mel Gibson and Danny Glover.

Most new series face the same issues starting out. But as an adaptation of an iconic film, Lethal Weapon faces a unique set of challenges, the most obvious being that its success will hinge greatly on the chemistry between the show's two leading men. Without that, the series is just another generic cop drama on a network that's been trying (unsuccessfully) to put a spin on the genre for years. With Lethal Weapon, Fox may finally have a chance at success. Still, for executive producer Matt Miller, casting the roles of Riggs and Murtaugh was a major undertaking.

"It was a challenge because two guys played these roles really really famously, and to find people that were not only going to have chemistry with each other but make you forget about those two was kind of the biggest challenge of the pilot," says Miller, whose first stop on the road to casting was to speak to Richard Donner, who directed each of the Lethal Weapon movies.

Lethal Weapon First Look: Meet the new Riggs and Murtaugh

"He said, 'Great. But if you don't have the guys, you're screwed.' So right off the bat, we knew that the casting was going to be everything," says Miller.

The roles of Riggs and Murtaugh eventually went to Clayne Crawford (Rectify) and seasoned actor Damon Wayans, Sr., respectively. The search for Murtaugh, the older of the two men and who most fans will fondly remember for "getting too old for this sh*t," was relatively smooth sailing, with Wayans signing on early in the process.

"I was thrilled ... [because] I knew I didn't have to worry about Murtaugh," says Miller. "Damon — as a performer, as an actor — brings such a different perspective to the role than Danny Glover does that when you're watching him on screen, you don't ever think, 'Oh, Danny Glover did it this way.' You're only watching Damon and you're sort of drawn into that performance."

Clayne Crawford, Damon Wayans Sr., Jordana Brewster, Johnathan Fernandez, Kevin Rahm and Keesha Sharp, <em>Lethal Weapon</em>Clayne Crawford, Damon Wayans Sr., Jordana Brewster, Johnathan Fernandez, Kevin Rahm and Keesha Sharp, Lethal Weapon

So with their Murtaugh ready to go, Miller and fellow executive producer McG turned their sights on the more difficult task of finding the right man to play Riggs. They needed someone who could handle the crazy world of Los Angeles but who also felt at home in Texas, where Riggs lived before his wife and unborn child were killed and before he met Murtaugh. According to Miller, that also meant finding someone who could distinguish Riggs from the way Gibson played the character.

"Every actor who came in, whether they knew it or not, they were sort of doing a Mel Gibson imitation, and that was never going to work," says Miller, noting that the production team searched from the U.S. to Australia and everywhere in between without any luck.

"We found [Crawford] on an independent movie that he made, and the casting director kind of ran in and said, 'I think I found Riggs,'" recalls Miller. "And we watched this and we were like, 'Great. Where is he?' And they said, 'He's on a farm in Alabama, with his family and horses and whatever else they got out there.'"

Crawford was coming off a four-season journey on Sundance's little-seen but critically acclaimed drama Rectify, and he wasn't sure about the terrifying prospect of stepping into a role as iconic as Martin Riggs.

"I thought everyone involved with the Lethal Weapon franchise had just done such a wonderful job, including, obviously, Mel Gibson, who really kind of dominated this role and didn't leave a lot of the meat on the bone. So I didn't even want to read the script," says Crawford. "But I read the material and I couldn't ... say no to a man that was... so broken, but yet was kind of like a hero and trying to do the right thing. And it just kind of grabbed me immediately, [it was] so terrifying."

Although he overcame his initial hesitation about taking on the role, Crawford is still apprehensive about how the show will be perceived.

"It's scary going to work every day. I don't know how we're going to maintain this," says Crawford. "But I have confidence in Matt Miller and McG and, of course, everyone at Warner Bros. and FOX that we're going to give it our best effort and we're going to leave it all on the field, for better or worse."

Lethal Weapon premieres Wednesday, Sept. 21 at 8/7c on Fox.