Eric McCormack to Diddy's Son ... Gay Role Could Change Your Life

If Diddy's son doesn't start stretching his mind, he could miss out on the role of a lifetime -- even if it's a gay role -- according to Eric McCormack ... who should know.

Quincy Combs told us he would have passed on playing the gay character Jamal on "Empire" because he didn't have enough experience as an actor. Considering how popular the show became, Eric thinks Quincy might have shot himself in the foot.

Eric played Will on "Will & Grace" -- which worked out pretty well for him -- and thinks Quincy's just not pushing himself. As he put it, "I've played murderers, and I never killed anybody."

Solid metaphor.