LOS ANGELES—Matt Damon looks young for 39, but as he edges closer to middle age, he is seeking projects that have a little weight. He found one earlier this year in The Informant!, a film that has inspired some Oscar buzz for his portrayal of a corporate whistle blower. However, when he got a script from Clint Eastwood for Invictus, the story of how a rugby game helped to change the course of South African history, he thought as much about his height as he did about the weightiness of the material.

“When I read the script, I called Clint and said, ”˜I can’t believe this story really happened,’ ” he says in an L.A. hotel room. “He said he couldn’t believe it either. Then I went immediately to look up Francois [Pienaar, the rugby player Eastwood wanted him to portray] and I said, ”˜Clint, this guy is huge. I know we have never met, but I am 5-10.’ He started laughing and said, ”˜Oh, hell, don’t worry about that. Go worry about everything else.’ ”

South African national rugby team star Francois Pienaar was captain of the team during the 1990s, when apartheid ended and the country elected Nelson Mandela (played in the movie by Morgan Freeman) as president. Although both blacks and whites assumed that Mandela would seek revenge for his years in prison, he decided to heal the country by integrating it. Mandela knew that most South African blacks saw the national rugby team, the Springboks, as a symbol of apartheid, but he decided to use the team and the sport as catalysts for change. He met with Pienaar on the eve of the 1995 World Cup competition, which was going to be held in Johannesburg, and told him that he wanted to support the Springboks, but that he needed the team to make the best effort possible to help bring the country together. (The movie opens on Friday [December 11] in Vancouver.)

Damon began to get in shape to play rugby on-screen, and learned to speak with an accent months before the movie started principal photography. When he headed to South Africa to start shooting the film, his first stop was the house of the former team captain.

“I had about six months to get ready, and I worked hard on the accent and I trained physically to build myself up to pull off the illusion of being the captain of the South African team,” he says. “I look at every possible pitfall when I am doing a role, and at what can possibly blow the illusion, and then I look at ways of solving problems. So I made my little checklist of things I had to do and planned it out, and then I went to South Africa. Francois invited me to meet his wife and family, and so Morgan and I went to his house. I remember ringing the doorbell, and he answered and I looked up and the first thing I said was, ”˜I look much bigger on film.’ He gave me a big hug and took me into his house, and he became an invaluable resource for me. He let me ask all sorts of questions.

“Talking to him philosophically about things like leadership was very important. If you look at the structure of the script, you have the greatest leader of our time appealing to this other type of leader and saying, ”˜I need you to do this,’ and Francois understanding that the team had to exceed expectations because it was a metaphor for what the country was trying to do. He [Mandela] saw in Francois leadership and inner strength, and those were the kinds of things that I needed to get across. So there was a lot more to it than just lifting weights.”

Damon says that roles in films that address issues of human justice have always appealed to him. “I probably react more strongly to things that I feel will have social value. I saw this as a wonderful message to put out there. It is a completely nonpartisan message, one about healing and coming together, and it is an incredibly uplifting story. I think that is why it appealed to me. It is not like I said, ”˜I want to make a movie about this.’ I read this incredible script and it was about the greatest leader of the last 50 years. He was being played by Morgan Freeman, and Clint Eastwood was directing. So it was a pretty easy decision for me.”