Transcript for 'Southpaw' Star Jake Gyllenhaal KO's Times Square
Because I'm here with Jake gyllenhaal. Critics saying he delivers a into knockout performance in "Southp "Southpaw." You can key this scene. I was looking forward to just showing up, walking into the ring, and having him fall on the ground. I mean, I mean, I expected a hard fight, you know. I put my family through a lot. By the way, Leila, if you're watching, go to sleep, baby. I loved this film. Thank you, Jake. You're so -- so good to us. When you come here and the films that you're doing. I saw it this weekend. And we were talking in the break. It's one of the classic kind of boxing movies. But then it's also so incredibly different. A lot has been made about the transformation. You were all in, as you are in the ring right here. Yeah, we're in a ring right now. I don't know what's going to happen. It's a muf I have about family. About a father and a daughter. That's why I wanted to make it. Yeah, I had to learn how to box. I didn't want to look like an idiot. I trained five months for it. Five months? Yeah. A lot said about the situps and all that. But I didn't realize that the director, Antoine Fuqua trained with you? He trained with me. I did twice a day. He said this was about sacrifice. Sacrifice for the people we love. I'll be with you every time you get in the ring. I want to train with you every morning. It helped you evolve the character of Billy. Especially in the clip here, sometimes it was hard to ups because you're mumbling. That's part of who he is. Yeah, well part of it is he grew up in the foster care system. I don't think he ever had a model of a parent to learn how to be. He becomes a parent very early in life. He's really articulate in the ring. That's where he expresses himself. He doesn't exprez himself as well outside the ring. His wife is a rep zresentative for family. She's amazing, Rachel Mcadams. Forest Whitaker is in the movie. Oona Laurence. She was in Matilda. She's a great actor. Such a lovely girl. She would improvise with me. I was always physicfollowing her. She was much more skilled than I was. That's the beauty of the film. When you're in the ring. I know you're upset about this. People don't realize, there's no double in that ring. It's all you. Even when the back of you. Yes, yes. Antoine said to me herbally on. I want to show this movie like a real fight. I want to shoot it like an HBO fight. You need to be available all the time. I don't want double. There were no doubles. What about the first time you got the moneymaker, right here, smacked in the face? Actors need to be knocked around a little bit, to be honest. It's great profession, it's easy in a lot of ways. The more you can get close to the real thing, the more you can feel what it feels like -- it wasn't the best feeling. It happened a lot. It adds to the reality of the movie. And the reality of the move I have, too, the anger that Billy deals with. It helped him inside the rope. Got him in trouble outside. You said it was also a way for you the kind of tap into the anger that you may or may not have. Absolutely. It's -- to me, when I read it, it was a story about a guy who used his rage to get to the place early in his career where he got to. He can use it in the ring. It doesn't work outside the ring. It destroys his life in many ways. He has to relearn how the be a father without those things. For me, the greatest part of being an actor, you're able to explore feelings in a safe place. It's why I believe in the arts. I feel like arts and sports give kids a safe place to express themselves outside of, you know, where the world where the consequence can be very different. That's really you will straited in the film as well. So much I I want to tell people about. They have to seep it themselves. You'll be back next week. With oona. That will be a lucky time. We get you twice? You get oona Laurence. I get to hang out with her again. "Southpaw" in theaters on Friday.
This transcript has been automatically generated and may not be 100% accurate.