Hayek never really departed from the essential economic theory that he developed during the 1920s, although he expanded and deepened his analysis. - Alan O. Ebenstein

Hayek had high regard for Marx in technical economic theory and considered him a predecessor in his business cycle theory. [...] It was not in technical economic theory that the classical Austrians disagreed with Marx. So towering a figure in history is Marx that discussion of his thought in summary form is always difficult, for there is so much that he said and that others have said about him. At the same time, so tendentious, ill-spirited, and just plain wrong a thinker was Marx that it is surprising that he may have had some of the influence attributed to him. Hayek’s opposition to Marx was in the realm of practical political emanations from Marx’s thought. Here he considered Marx’s influence to have been wholly pernicious.

Expressed egotism is, of course, no reason necessarily to disregard someone’s work, but it is a warning signal. If someone can evaluate his work so poorly, is the work itself likely to be better? In many of his areas of intellectual interest, Popper’s work is wanting.
Hayek did more to advance Popper professionally early in his career than anyone else, and Popper remembered his personal debt to Hayek. Over the years, he wrote him a number of appreciative letters.

The question of Hayek’s relationship to the Chicago school of economics raises the anterior question of the Chicago school of economics itself.