The characters comprising this year’s SAG-nominated ensembles are based on either real people or memorable stage characters. So it’s safe to say casting directors had shoes of epic proportions to fill.

Rich Delia, who cast “Dallas Buyers Club” with Kerry Barden and Paul Schnee, says the fundamental challenge was finding actors who felt authentic. “When you’re playing people that are based on real people in such intense circumstances, you really want to cast people that have an understanding and a respect for that,” Delia says. “We really don’t want anyone to pull you out of the story.”

Similarly, “12 Years a Slave” — based on the memoir of Solomon Northup, a free man sold into slavery — also tells a harrowing tale of historic significance. “When you have a story that means so much to so many people, it’s daunting,” says casting directing Francine Maisler.

While this is an age-old challenge, other setbacks have become avoidable in recent years thanks to video chat Web services. Director David O. Russell became a fan of Skype as a casting tool following Jennifer Lawrence’s now-famous audition for “Silver Linings Playbook.” Lawrence didn’t have to audition this time around for “American Hustle,” but casting directors Mary Vernieu and Lindsay Graham did set up calls for the supporting cast.

“It takes some getting used to as far as having the director ‘Skyped in’ to the audition, but you still have the opportunity to connect in real time and make adjustments, which can often carry more weight than the director simply viewing a tape if they are in another city,” Vernieu and Graham said via email.

Case in point: Jared Leto’s Skype call with “Dallas” director Jean-Marc Vallee. The actor-turned-rocker landed the role of Rayon after tapping into the character during their video chat. “Rayon has a playfulness about her and a flirtation about her; I think that Jared showed up with that,” Dalia says. “There’s a light and a spark about Rayon, and Jared inhabits that as well.”

Barden, who also cast “August: Osage County” with partner Schnee, says that film’s casting was unusual in the sense that actors who hadn’t auditioned in years read for their parts (with the exceptions of Meryl Streep and Julia Roberts).

Maisler, on the other hand, relied on a more traditional, albeit daunting, casting practice. More than 1,000 actresses auditioned for the role of Patsey — a young slave abused by her owner — which Lupita Nyong’o ultimately nabbed. Director Steve McQueen has compared their search for the character to finding Scarlett O’Hara. “It’s not easy for anyone to walk off the street, into an office and immediately be in the appropriate mental state to deliver such a difficult performance,” Maisler says. “I would have (Nyong’o) do the scene over and over again and once she was getting to that point emotionally, I would push harder.”

In addition to Nyong’o’s breakout role, the SAG Awards-nominated cast performances also featured two comebacks: Leto in “Dallas” and Oprah Winfrey in “Lee Daniels’ The Butler.” All three nabbed SAG Awards supporting noms. “We said, ‘Look, (Leto’s) been focused on his music, but if ever someone was to come back for a role, this is the kind of role that someone wants to come back for,’” Dalia says. “Rayon truly is, I believe, the heart of the film. Jared, we felt, would really see the beauty in that character and not judge her.”

Meanwhile, Winfrey returned to acting after a 15-year hiatus. Director Lee Daniels recreated the character of the butler’s wife, Gloria Gaines, with her mind. Denzel Washington was initially in talks for the lead role, which eventually went to Forest Whitaker. Leah Daniels-Butler (the helmer’s sister), who cast the film with Billy Hopkins, says the greatest obstacle wasn’t persuading Winfrey to come on board, but selecting the film’s five presidents. “You had to find the actor that sort of resembled who they were playing, but also didn’t distract the audience by who they really were,” Daniels-Butler says. “Eisenhower was the last president to get cast because it was really hard to find someone that resembled him, with a name value and could also pull off the performance.” Robin Williams ultimately got the part. Liam Neeson and Hugh Jackman were in talks to play presidents in early stages.

For many of these films, choosing the lead created a domino effect that allowed the supporting cast to fall into place. For instance, Streep set the bar high for the rest of “August”s stars, while Roberts’ casting as her eldest daughter set age constraints for the other actresses. After being dormant for more than a decade “Dallas” was revived when Matthew McConaughey signed on as the lead (director Marc Forster and Brad Pitt were initially attached). His weight loss and promotional tour were driving forces in getting the film produced after funding fell through several times.

When it came to casting “Hustle,” Russell dipped into his trusted alumni network. “David is very loyal and has almost a repertoire of actors he has worked with over the years so he always has his people in mind throughout the process,” says Vernieu, who’s cast almost every Russell film since 1999. “We were not able to release any sides to the actors as the script was being rewritten, so all the auditions for the supporting roles were improv.”


What: 20th annual

SAG Awards

When: 5 p.m. PT/

8 p.m. ET Jan. 18

Where: Shrine Exposition Center