Speaking with ET's Kevin Frazier, Gyllenhaal opened up about the paternal instinct that informed his Southpaw character, explaining, "I am not a father yet, but it is definitely a dream of mine, should I be lucky to have that to happen."
Gyllenhaal added that the actress who plays his young daughter in the film, Oona Laurence, made him even more excited about the idea of being a dad.
"I have nieces who I love deeply and I have children in my life I love deeply, but when I meet Oona for the first time, I just fell for her," Gyllenhaal shared. "Your heart opens up to her."
The actor said that his young co-star actually helped him develop and guide his character and his performance.
"When I started acting with her too, she was the one who was guiding me. We improved a lot, and she would make choices, I would just follow her in an improv, and that's the dynamic," Gyllenhaal recounted.
Check out the video to hear more from the celebrated star about his super-talented co-star, and why he wants to be a dad.