play a small role (in something)

1. Literally, to act out a very small, inconsequential role (in some piece of drama, film, or television). I originally started off playing a small role in the sitcom, but over the years the character became wildly popular and really launched my career. A: "I heard you're in the latest Schwarzenegger movie, right?" B: "Yeah, I'm just playing a small role, though."

2. By extension, to have a very small, inconsequential role (in some resultant situation, action, event, outcome, etc.). I know you feel like you only played a small role in our victory today, but you were just as important out there as everyone else on the team. A: "I suppose those long, 12-hour days were why you quit, huh?" B: "Actually, those only played a small role—it was mostly just because I hated my boss."