Neil Bahadur’s review published on Letterboxd:
"I can see my money is still in your pocket, which is from the yield of my labour."
Renoir's quote “A director makes only one movie in his life. Then he breaks it into pieces and makes it again,” is more applicable to Mann than probably any other filmmaker. So whats interesting here, is what Mann doesn't do again over time. Firstly, James Caan has more freedom than any other Mann lead would ever have, and it's a testament to his and Tuesday Weld's ability that they're able to make Mann's eliptical dialogue sound totally natural (not that the opposite is a bad thing!) The script itself is more direct and dialogue driven than any Mann film in the future would be, and curiously, it's striking less for its own relation to this work, and more because of what it reveals about Mann's future films (see the above quote)
Also, interesting here is that often a "Mann hero" is defined by a rise into self-identification (with the exception of Blackhat, which I think is more about collectives rather than individuals) and gaining a kind of new consciousness. With Thief though, James Caan's Frank is defined by his failure to rise into self-identification.
For me however, the biggest surprise came with Leo's character. Mann has always talked about the influence of 20's German Expressionism on his films in interviews, specifically his love of Pabst and Murnau, and included Murnau's Faust in his Sight and Sound list from 2002. Thief is basically a remake of Faust, Mann simply updating the film to apply to 20th century late capitalism. I think that's the key to Mann, perhaps: The merging of aestheticism and Marxist critique.