Clifton Collins Jr. doesn’t believe in half measures.

For “Jockey,” an intimate drama about an aging rider, the actor shut himself off from friends and family to get in the mindset of his loner character. He needed to access the pain and emotional baggage of a man who is grappling with failing health, as well as the arrival of a younger racer (Moises Arias) who claims to be his son.

“I cut myself off from the world,” Collins tells Variety shortly before “Jockey” premiered to stellar reviews at this year’s Sundance. “I talked to three people the entire time I was gone. I like to go deep.”

He also pushed his body to the breaking point, shedding 20 pounds from his already-thin frame in order to replicate the slender build of a professional jockey. Doing that required adhering to a spartan diet.

“I had a stack of five or eight almonds a day and it was like my life line,” Collins remembers. “On occasion, I’d sneak in a peanut M&M and I’d still feel a little bit of guilt.”

One thing that Collins refused to do was binge and purge, or in jockey parlance “flipping,” one of the extreme and dangerous methods that professional riders use in order to meet their brutal weight requirements.

“I like to go pretty Method, but you’ve got to have certain boundaries,” Collins says, admitting that some riders hinted he should try the approach.

The actor had experience riding horses on past films, but he still left most of the heavy lifting to the real jockeys. Horse racing was just too risky to justify getting in the saddle for key sequences.

“When those horses hear that bell, when they hear that door open, they want to do what they want to do and that’s dragster run,” says Collins. “It’s terrifying.”

“Jockey” was filmed on a minuscule budget at Turf Paradise, a functioning track in Phoenix and the real-world setting helped Collins immerse himself more deeply in the role. He hung out with actual riders, befriending them and soaking in the way they walked and talked, and even got heckled by fans. The goal was to blend in as much as possible, something that was helped by the skeletal production apparatus.

“We wanted to be a part of the environment, so it helped to not have trailers, to not have giant lights,” says Collins. “It helped to not have hair and makeup or cast chairs with your name on them.”

It was, Collins says, a “labor of love in the truest sense,” one that reunited him with director Clint Bentley and his co-writer Greg Kwedar. The three had previously collaborated on the 2016 thriller “Transpecos” which Kwedar directed from a script co-written with Bentley. It was also a rare opportunity for Collins, best known for supporting turns in the likes of “Capote” or “Westworld,” to take a starring role. He insists that didn’t enter his frame of mind.

“It’s got nothing to do with the creative process,” says Collins. “On an indie you don’t have time to look at where you are on the call sheet. It’s just what time do I have to be there?”

Yet it’s Collins’ performance that’s earned the lion’s share of the praise from critics and is also a major reason that Sony Pictures Classics swept in and bought the film out of Sundance. The specialty label behind “Whiplash” and “Call Me By Your Name” hopes to push Collins into next year’s awards race. Collins attracted Oscar buzz for 2005’s “Capote,” playing murderer Perry Smith, but fell short of a nomination. If the studio pulls it off, an Academy Award nod would be long overdue recognition for Collins, who does consistently solid work without ever seeming to have found that one role to move him out of “that guy” roles and propel him to the A-list.

“I can almost guarantee you that I’ll deliver a spectacular character,” says Collins. “I love creating these characters. I get off on the research, but its hard. It’s a lot of hand-to-mouth. It’s, oh I got a check. I can pay for this or I can pay for that.’ And sometimes you create a fantastic character and next thing you know here comes another character that’s similar but not be quite as good.”

Next up for Collins is a supporting turn in Guillermo del Toro’s “Nightmare Alley,” a noirish story set in the world of carnivals, conmen, and grifters. It’s also a period piece, unfolding in the post-World War II era. For Collins, the film was also an opportunity to think more deeply about his grandfather, Pedro Gonzalez Gonzalez, a character actor who appeared in everything from Groucho Marx quiz show “You Bet Your Life” to “Rio Bravo.”

“Guillermo pushed me over the top and kind of made me recognize my legacy on a deeper level,” says Collins, who spoke to the director about Howard Hawkes, William Wellman and some of the other legendary filmmakers with whom his grandfather worked.

Gonzalez Gonzalez died in 2006, but Collins has been going through old archival material and poring over interviews with his grandfather as he writes a script about his life. As a performer, Gonzalez Gonzalez was known for sewing hubcaps into his pants and playing them with a mallet. That detail led to some serious temptation for Collins on the set of “Nightmare Alley,” where many of the cars around him were old Ford pickups from the time when Gonzalez Gonzalez was making a name for himself.

“I was staring at these hubcaps, and I just really wanted to steal them,” says Collins, lowering his voice in a conspiratorial manner. “Even now I’m acting like I’m worried I’ll get caught.”