Mitchum really hated McQueen for some reason. He was a seasoned vet when Steve came along as a journeyman actor, the next big thing, etc... It's funny 'cause you never, (or rarely), see big-name actors bad-mouthing each other nowadays.
One of his typical comments was, "That kid sure doesn't bring much brains to the party..."
FWIW, I could not disagree more. Steve McQueen
was a mininalist, and an existentialist but what he did and the way he did it simply cannot be matched. A lot of actors wish it could. He was more like a jazz musician or a painter than he was like most actors.
Mitchum was good at what he did but he could not touch McQueen, IMO.
Can you tell that I'm a fan?