Lackluster Brando performance?
I'm not so sure about that.
While John Saxon was amazingly impressive, Brando effortlessly manage to come out as the best in my opinion. His confrontation with Saxon's character was the highlight of Brando's performance; now, you can disagree with the fact that he was great, but in that particular scene, Brando shined immensely.
There was nothing dull or unconvincing about Brando; despite his lack of interest in the film in real life, he turned out to be the highlight most definitely. Saxon came a close second.
Go ahead... make my sandwich.