The Godfather influence

I never saw this film until I rented it from Netflix. It was 2 hours and 48 minutes long and I had to watch it the second time in order to really appreciate it. While watching it, for some reason, I was thinking of Francis Coppola ( The Godfather ) director and at the end, watching the credits, sure enough his name came up as co-director or co-producer with Di Nero. I could see the influence he had with Di Nero. Now as for the film itself, first I saw the actor Keir Dullea of the big hit way back, 1969... "2001" and I did see him briefly at the scene where Damon, meets Jolie, but he had no lines that I was aware of...so why was he in this picture at all, and the same goes for Pesci, other than the fact that Di Nero is loyal to his old time buddies and figured to throw him in also.