The thread started with this question: "What is THE or at least ONE of the most stunning single performances in track & field history? The "stunning" quality could be either because of an upset or because of pure performance.
No one has so far responded to the upset alternative with Harrison Dillard's 100m dash victory at 1948 Olympics in London.
Dillard, known then primarily as a hurdler, did not make the USA team in his event after tangling with a barrier in the USA trials. But he went to London as a 100m dash competitor and on 31 July 1947 upset favorites such as Mel Patton, Barney Ewell, and Lloyd LaBeach.
Postscript(s): Patton won the OG 200m on 3 August 1948 -- and Dillard came back four years later to win the 110m hurdles in Olympic record time at Helsinki on 24 July 1952.