Actors Abe Vigoda and Al Lettieri had recently appeared in Francis Ford Coppola's The Godfather (1972).
Second movie where Al Lettieri says that a Don is "slippin'" (as in, losing his edge). The first was about Marlon Brando in The Godfather, and here it's about Anthony Quinn (both Brando and Quinn starred in Viva Zapata decades earlier).
Uncredited actor Carlos Romero's slumped over/dead body adorns the poster.