Mark Wahlberg has been preparing his entire life for his latest role as bad boy pugilist turned Catholic priest, Father Stuart Long.

“I’ve gotten so much joy and comfort from my faith,” Wahlberg said last week from the Four Seasons Philadelphia. “It’s always been my security blanket. Being able to show that through this film and talk about my own personal story is something I’m excited to do.”

Father Stu will open in theaters on Wednesday during Holy Week, the commemoration of the last days of Christ, ending on Easter Sunday. Wahlberg, 51, is a practicing Catholic who attends Sunday Mass at St. Patrick’s in Rittenhouse Square when he’s in Philadelphia filming movies. The timing of this release is not a coincidence.

The actor was in town to screen Father Stu to a group of clergy and laity at Villanova University, part of a six-city tour. In many ways Philadelphia, Wahlberg said, reminds him of South Boston where he grew up. “I have a number of friends and family here,” Wahlberg said. “I consider myself an honorary Eagle.”

Father Stu, a biopic starring Jacki Weaver and Mel Gibson as Long’s estranged parents, is a true story about faith, determination, redemption, and reconciliation. We meet Long in the mid-1980s. He’s an aging, agnostic boxer living in Montana with a surly mouth and a bad attitude. He takes a beat down in the ring and his doctors advise him to quit, so he picks up and moves to Los Angeles to pursue a career in acting.

Life happens: He falls in love with a devout Catholic, converts to Catholicism, has a near-death experience and after that decides to become a priest. But the rector of the seminary refuses to admit him because of his past.

Long argues many of the church’s most important historical figures — St. Matthew, St. Augustine, and St. Francis — were reformed. “Besides if the church doesn’t celebrate the capacity for change,” Long asked, “What does it stand for?”

After a short time in the seminary, he’s diagnosed with inclusion body myositis, a rare and fatal autoimmune disease that causes muscle atrophy and shuts down bodily functions. Eventually he’s ordained but is only a priest for four years, before dying at an assisted-living facility in Montana in 2014 at 50.

Former priest James Flavin makes a cameo as one of the bishops who ordains Long. Flavin was one of Wahlberg’s parish priests when Wahlberg was growing up in Boston. Wahlberg credits Flavin for helping him build his faith foundation. However, Flavin is a controversial figure in Philadelphia’s Catholic community because at one time he was president of the St. John Vianney Center in Downingtown, which has been named in several grand jury reports investigating clergy child sex-abuse cases.

Wahlberg learned of Long’s story seven years ago while having dinner with two priests. He invested in the project and began working on it. Gibson’s girlfriend, Rosalind Ross, wrote the screenplay, and directs the film. Wahlberg’s transformation to the ailing Father Stu is so complete, it’s only a matter of time before the Oscar buzz begins.

Before Wahlberg became a rapper, actor, husband to model Rhea Durham, and father of four, he was a gang member, a coke addict, and served 45 days in jail for assaulting two Asian men in an attempted robbery turned hate crime. Today, he is an Academy Award-nominated actor and philanthropist whose eponymous foundation helps troubled youth.

“The message of this film is that no one is beyond repentance,” Wahlberg said.

I chatted with Wahlberg about the film’s message. The interview has been edited for clarity.

What did you admire most about Father Stu’s story?

His dedication and commitment to serving God. It was remarkable the amount of people he touched in the short time that he was a priest. I got to meet the people and see how many people he touched in such a profound way. It was really remarkable. His life experience was invaluable when he was ministering to them. They were all going through something Stu had gone through. He utilized all that real-life experience when communicating to them, it was really powerful.

Was there a time when your faith was shaky?

Oh yes, definitely. Especially during COVID. I got COVID myself and I went through a bout of depression that I never dealt with before. The only way I got through it: I start my day every day on my hands and knees thanking God. It’s a good reminder of the path I needed to be on and what I needed to put my trust and focus into the Lord.

What did you bring from your real life to this role?

Well, many things, many things. My dad had a stroke and I watched his physical deterioration. I saw first hand what Stu must have gone through and all of the things, the good, the bad, and everything in between helped me see that faith is at the core of my foundation.

Tell me about your transformation in this movie?

Packing on that amount of weight in such a short amount of time was difficult. (Wahlberg put on 30 pounds for the role and ate between 7,000 and 11,000 calories a day, including glasses of olive oil.) But it was important to Stu’s journey because he was such a strong, fit guy. For him to lose that physicality and gain the strength of a thousand men through his face is what I wanted audiences to see and understand, to see how quickly the disease had taken its effect and how the Lord really empowered him.

Did this film strengthen your commitment to the power of forgiveness?

I try to judge people based on the experiences I have with them. I did a lot of things in my life and when I started focusing on my faith and doing good works, good things started happening … I know people who never had a chance in life. They were caught up in drugs, violence, and incarcerated and if they feel like nobody cares, what are they working for? Let’s not be the judge. There is only one judge. We know who that is.